Category: Behavioral Ecology

  • Fall Migrations Along Onslow County

    Fall Migrations Along Onslow County

    Late August does not look much like fall along the Onslow County coast.

    The sand is still hot. Afternoon thunderstorms still build over the mainland. The ocean can remain warm enough that stepping into it hardly feels like relief.

    But beneath the surface, fall has already begun.

    Fish that spent summer scattered through sounds, creeks, reefs, and nearshore water begin gathering. Shrimp start working their way out of nursery creeks. Mature female blue crabs move toward saltier water. Schools of mullet begin appearing along the beaches. Sharks that spent the warmer months farther north or inside coastal waters begin shifting south or offshore.

    Above them, the birds begin changing too.

    Some are preparing to leave. Others are arriving from places hundreds or thousands of miles away. Still others simply become more noticeable because suddenly there is food everywhere.

    What looks from shore like a few gulls working over the water, a school of baitfish flashing beside a pier, or pelicans repeatedly diving beyond the breakers is part of something much larger.

    For a few months each fall, the food web itself begins to move.

    When the Water Begins to Change

    Animals do not wait for a date on the calendar. Along the coast, fall arrives through changes in water temperature and daylight, but also through salinity, currents, rainfall, food availability, and the timing of reproduction. Different species respond to different combinations of those signals, which means the seasonal movement beginning beneath the surface is not one migration triggered in one way.

    For some animals, cooling water begins narrowing where they can comfortably remain. King mackerel (Scomberomorus cavalla) favor warm coastal water and become less common as temperatures fall much below about 68°F, while cobia (Rachycentron canadum) begin leaving northern summer habitats as water cools through roughly the same range. Spotted seatrout (Cynoscion nebulosus) respond differently. Rather than leaving our estuaries altogether, they begin shifting toward creeks, channels, and deeper water where a few additional feet of depth can provide protection from the colder temperatures still to come (North Carolina Division of Marine Fisheries, 2022; Jensen & Graves, 2020; Ellis, Buckel, & Hightower, 2017; Ellis, Buckel, Hightower, & Poland, 2017).

    King mackerel (Scomberomorus cavalla), a warm-water coastal fish that becomes less common as fall temperatures drop. | Image credit: Sylvain Le Bris, iNaturalist
    King mackerel (Scomberomorus cavalla), a warm-water coastal fish that becomes less common as fall temperatures drop. | Image credit: Sylvain Le Bris, iNaturalist

    Temperature can work together with another signal that changes every year whether the weather feels like fall or not: shortening daylight. Blacktip and sandbar sharks moving along the western Atlantic begin their southward migration as sea-surface temperatures change and the days grow shorter, leaving northern and Mid-Atlantic summer habitats and gradually shifting toward the South Atlantic Bight and Florida for winter and spring (Manz et al., 2025).

    For other animals, autumn movement is tied less to escaping cooling water than to reaching the next stage of their life cycle. Southern flounder (Paralichthys lethostigma) spend their first years in estuarine waters, where shallow sounds, rivers, and creeks provide nursery and feeding habitat. Females begin maturing surprisingly early: some are reproductively mature by age one, most by age two, and nearly all by age three. Immature fish can remain within the estuary through winter, but once mature, southern flounder begin joining the fall movement through the inlets and toward offshore spawning grounds (Midway & Scharf, 2012; Craig et al., 2015).

    That means fish of different ages can occupy the same estuary through summer and then take different paths as fall develops. A young flounder may remain behind while an older fish that spent the season feeding in the same system begins moving toward the ocean.

    So while late-August water may still feel thoroughly summerlike to someone standing waist-deep at Topsail, the animals beneath the surface are already responding to a season that is only beginning to become visible above it.

    One of the first clues may simply be a fish jumping beside you.

    The Mullet Begin to Run

    Striped, or sea, mullet (Mugil cephalus) spend much of the warmer season feeding throughout estuaries, sounds, tidal creeks, and protected coastal waters. By late summer, however, their movements begin to change. In North Carolina, striped mullet travel most actively between August and November as mature fish leave rivers, sounds, and tidal creeks for marine spawning habitat. Their journey carries them through the inlets and offshore into the South Atlantic Bight, with spawning habitat extending from nearshore waters toward the outer continental shelf where shelf water meets the influence of the Gulf Stream (Bacheler et al., 2005). For fish that spent the summer inside an estuary, that is a considerable change in geography, but still a relatively regional migration compared with species that will later continue much farther south along the Atlantic coast.

    Striped mullet (Mugil cephalus) schooling in shallow coastal water. | Image credit: rangerval, iNaturalist
    Striped mullet (Mugil cephalus) schooling in shallow coastal water. | Image credit: rangerval, iNaturalist

    They begin making that seasonal journey relatively young. About half of North Carolina striped mullet are reproductively mature by age one, although maturity varies among individuals, and older adults may return to estuarine habitats after spawning. Rather than leaving the estuary permanently as they mature, they move between estuarine feeding grounds and marine spawning habitat as part of a seasonal cycle (Bichy, 2004; Bacheler et al., 2005).

    For beachgoers, this can become one of the easiest fall migrations to notice. Fish that spent summer spread through rivers, creeks, and sounds begin collecting into increasingly conspicuous schools as they move toward inlets and coastal water. Once along the ocean beach, dense schools may travel remarkably close to shore, sometimes darkening the shallows or stretching along the surf zone beyond what can be seen from one spot. Mullet are frequent jumpers as well, so a school may first reveal itself as silver fish repeatedly breaking the surface.
    By the time those schools reach the inlet and beach, they are carrying more than themselves with them. Striped mullet feed low in the food web, consuming algae, detritus, and organic material associated with estuarine sediments. As thousands of them move out of the estuary, that stored production moves with them and becomes available to the larger fishes, sharks, and birds that feed along the coast (Bacheler et al., 2005).

    Those predators are already moving through the same corridor. Bluefish (Pomatomus saltatrix) feed heavily on schooling fishes such as mullet, menhaden, and silversides. Spanish mackerel (Scomberomorus maculatus) work schools of anchovies and other small baitfish, while blacktip sharks (Carcharhinus limbatus) and spinner sharks (Carcharhinus brevipinna) take advantage of dense concentrations of coastal prey.

    The fall mullet run is therefore more than thousands of fish leaving an estuary. It is estuarine production moving through the inlet and onto the beach, where it begins to intersect with predators following their own seasonal routes.

    That intersection is what makes the migration suddenly visible. A school that might otherwise pass unnoticed can tighten near shore as bluefish, mackerel, sharks, and birds begin responding to the same moving concentration of prey.

    Spanish Mackerel, Bluefish, and the Surface Chase

    Sometimes the easiest way to find a migration is not to look for the animals themselves, but for what happens to the water when they arrive.

    Spanish mackerel (Scomberomorus maculatus) spend the warmer months moving north along the Atlantic coast, reaching North Carolina in spring and remaining through summer and early fall while coastal water stays above roughly 68°F. As that warm-water window begins closing, they turn south again toward winter habitat off Florida, feeding heavily along the way on anchovies, silversides, menhaden, mullet, and other small schooling fishes (North Carolina Division of Marine Fisheries, 2026; Sutherland & Fable, 1980).

    Spanish mackerel (Scomberomorus maculatus) traveling in a dense school. | Image credit: Shutterstock
    Spanish mackerel (Scomberomorus maculatus) traveling in a dense school. | Image credit: Shutterstock

    Bluefish (Pomatomus saltatrix) are moving through the same changing coast, but their fall pattern varies with age. Smaller bluefish tend to migrate south along the shoreline as water cools, while larger adults make more of an inshore-to-offshore shift. Farther north, fall movement begins as water drops into roughly the mid-50s Fahrenheit, gradually carrying fish into the warmer coastal waters to the south (Lund & Maltezos, 1970).
    By the time those movements reach the Carolina coast, they are crossing water already crowded with prey. Anchovies, silversides, juvenile menhaden, and other tiny schooling fishes—many of the fishes beachgoers collectively call “glass minnows”—can become compressed near the surface, and even wash onto shore, as mackerel and bluefish strike through the schools from below.

    Little tunny (Euthynnus alletteratus), better known locally as false albacore, can join that fall activity around inlets and nearshore waters as well. They too make seasonal movements along the Atlantic coast, shifting north through the warmer part of the year and south again through fall and winter while feeding in fast-moving schools (North Carolina Division of Marine Fisheries, 2026).

    Little tunny (Euthynnus alletteratus), also known as false albacore, moving in a feeding school. | Image credit: aurelpap, iNaturalist
    Little tunny (Euthynnus alletteratus), also known as false albacore, moving in a feeding school. | Image credit: aurelpap, iNaturalist

    From the beach, separating one predator from another may be nearly impossible. What becomes visible instead is the chase. A patch of otherwise smooth ocean suddenly begins to boil as tiny fish scatter across the surface. Gulls and terns converge overhead, pelicans turn toward the commotion, and dark backs or silver flashes cut through the school below.

    Sometimes the entire event moves several hundred yards down the beach within minutes.

    And the animals doing the chasing are still part of the food web themselves. Spanish mackerel and bluefish may be predators here, but both can become prey for larger sharks and tunas farther up the same moving chain. A small fish feeding on plankton becomes food for a mackerel; that mackerel may later become food for a shark.

    Fall has compressed several levels of the food web into the same patch of water, and for a few minutes the whole thing becomes visible from shore.

    The Sharks Following Fall

    Shark migration can sound dramatic because sharks are dramatic animals.

    Ecologically, however, their fall movements make perfect sense. Food is moving, water temperature is changing, nursery seasons are ending, and remaining in shallow water becomes increasingly expensive for animals whose body temperature largely follows the environment around them.

    Blacktip sharks (Carcharhinus limbatus) and spinner sharks (Carcharhinus brevipinna) are warm-water coastal sharks frequently associated with schools of mullet, menhaden, and other fishes.

    Blacktip (Carcharhinus limbatus) and spinner sharks (Carcharhinus brevipinna) can look very similar; fin markings and body proportions help separate the two. | Image credit: Bowers & Kaijiura, 2023
    Blacktip (Carcharhinus limbatus) and spinner sharks (Carcharhinus brevipinna) can look very similar; fin markings and body proportions help separate the two. | Image credit: Bowers & Kaijiura, 2023

    As coastal waters cool, these highly mobile sharks begin shifting south. For blacktips, that can mean a substantial journey: sharks that spent the warmer months along the Carolinas and farther north move down the Atlantic coast toward Florida, with large winter aggregations forming in the warm coastal waters of southeast Florida. Spinner sharks also shift south as autumn progresses, although exactly how their seasonal routes connect Carolina summer habitat with winter habitat farther south is less clearly understood (Manz et al., 2025).
    Their movement is not caused by prey alone. Temperature and the gradually shortening length of the day contribute to the timing of autumn migration, while concentrations of prey can influence where sharks pause and feed along the route (Manz et al., 2025). That shortening daylight is the actual span between sunrise and sunset—not the hour shown on our clocks. The gradual loss of daylight from late summer into fall provides a predictable seasonal signal even when water temperatures vary from one year to the next.

    The shallow coastal habitats these sharks use during migration are also important much earlier in life. Blacktip pups are born in protected nursery areas away from most adults, and young sharks can remain associated with shallow coastal habitat for several years as they grow. Males generally reach maturity around four to five years old, while females mature closer to six or seven; spinner sharks follow a similarly slow timetable, with females maturing later than males (Carlson et al., 2006; NOAA Fisheries, 2017).

    That means the shallow water along the coast is not simply a birthplace young sharks immediately leave behind. It can remain part of their world through several juvenile years before the broader seasonal movements of adulthood become established. Exactly how strongly young sharks remain connected to individual nursery areas is still being studied, but nursery habitat can shape where they spend some of the most vulnerable years of their lives (Heupel et al., 2007; NOAA Fisheries, 2017, 2024).

    Around New River Inlet and the beaches of Topsail, those later seasonal movements begin intersecting with the migrations already underway. Schools of mullet, Spanish mackerel, and other coastal fishes can create concentrated feeding opportunities along the same corridor, and both blacktips and spinner sharks may breach during fast pursuits, with spinner sharks sometimes twisting through the air in the leaps that gave the species its name (Bangley, 2014).

    A beachgoer watching a fall bait ball may therefore be seeing several stages of the coastal food web converge in the same narrow stretch of water.

    Atlantic sharpnose sharks (Rhizoprionodon terraenovae) use shallow coastal waters, sounds, bays, and estuaries throughout the warmer months. Adults are generally only a few feet long and feed on small fishes, shrimp, crabs, squid, and other coastal prey (Bethea et al., 2006; Roskar et al., 2024).

    Their fall movement is much smaller in scale than the southward migration of blacktips. During summer, Atlantic sharpnose are abundant in the shallow nearshore waters of Onslow Bay, where both immature and mature sharks occur and pups are likely born. As autumn progresses, they become less common in those shallow areas and shift toward deeper coastal habitat. Adults have even been found using offshore wrecks in North Carolina during winter before returning toward shallower water in spring (Roskar et al., 2024).

    So for Atlantic sharpnose, fall may mean moving offshore without leaving the region entirely. Predation does not disappear from the coastal food web; it simply shifts into a different part of it.

    Atlantic sharpnose shark (Rhizoprionodon terraenovae), a small coastal shark common in North Carolina’s warmer months. | Image credit: Virginia Institute of Marine Science
    Atlantic sharpnose shark (Rhizoprionodon terraenovae), a small coastal shark common in North Carolina’s warmer months. | Image credit: Virginia Institute of Marine Science

    Sandbar sharks (Carcharhinus plumbeus) show how different that scale can become. Young sandbars spend the warmer months in shallow nursery habitat farther north along the Mid-Atlantic, then move offshore and south during late September and October. Many repeat that seasonal route for several years as juveniles, wintering from North Carolina toward Florida before returning north in spring. As they grow, the journey expands, with older sandbars ranging from southern New England to Florida and Cuba (Merson & Pratt, 2001; McCandless et al., 2007; Kohler et al., 1998).

    Their autumn departure is tied closely to cooling water and shortening day length, while prey encountered along the route determines where they may stop and feed (Manz et al., 2025).

    Sandbar sharks (Carcharhinus plumbeus), a large coastal species that shifts south and offshore as fall progresses. | Image credit: Simon Peggs, iNaturalist
    Sandbar sharks (Carcharhinus plumbeus), a large coastal species that shifts south and offshore as fall progresses. | Image credit: Simon Peggs, iNaturalist

    Off Onslow County, artificial reefs and natural hard-bottom habitats add patches of structure to that broader migration corridor. AR-342, the Onslow Bay Saltwater Fishing Club Reef, lies in about 49 feet of water and is one such patch where fishes and other prey can concentrate along the shelf (North Carolina Division of Marine Fisheries, 2017).

    A reef does not have to be an animal’s destination to matter. Sometimes it is simply a place to feed before the migration continues.

    AR-342, the Onslow Bay Saltwater Fishing Club Reef, shown within the nearshore reef network off Onslow County. | Image credit: NC Division of Marine Fisheries
    AR-342, the Onslow Bay Saltwater Fishing Club Reef, shown within the nearshore reef network off Onslow County. | Image credit: NC Division of Marine Fisheries

    Cobia and the Last Warm-Water Feeding

    Cobia (Rachycentron canadum) are another warm-season visitor beginning to run out of time. During spring and summer they move north along the Atlantic coast, using coastal and offshore waters from the Carolinas into Chesapeake Bay and farther north. They favor warm water, generally around 68–86°F, and as autumn temperatures begin slipping toward the lower end of that range, they start shifting offshore and south toward warmer winter habitat (Jensen & Graves, 2020).

    Cobia (Rachycentron canadum), a warm-water coastal fish that begins shifting offshore and south as autumn temperatures cool. | Image credit: georgeh04, iNaturalist
    Cobia (Rachycentron canadum), a warm-water coastal fish that begins shifting offshore and south as autumn temperatures cool. | Image credit: georgeh04, iNaturalist

    That places coastal North Carolina somewhere in the middle of the journey. The cobia moving through our waters are not necessarily arriving for winter or leaving from a summer home here. 

    For many, this stretch of coast is part of the route between the two.

    Along the way, structure matters. Buoys, wrecks, reefs, and artificial reefs can gather baitfish and other prey into small pockets of activity in otherwise open water, giving a traveling cobia a place to feed before continuing south (Jensen & Graves, 2020). A reef that holds feeding cobia may also be busy with reef fishes, passing mackerel, schools of bait, and other predators using the same patch of water for their own reasons.

    By fall, the coast begins to feel less like a collection of separate habitats and more like a series of connected stopping places along the migration route.

    Flounder Leave Through the Bottom

    Not every migration announces itself at the surface. Some of the most important fall movement in Onslow County happens quietly along the bottom.

    Southern (left) and summer flounder (right) both spend much of their early lives over shallow estuarine and coastal bottoms before mature fish move offshore to spawn. | Image credits: J. Weferling, iNaturalist (left); harrier, iNaturalist (right)Southern (left) and summer flounder (right) both spend much of their early lives over shallow estuarine and coastal bottoms before mature fish move offshore to spawn. | Image credits: J. Weferling, iNaturalist (left); harrier, iNaturalist (right)
    Southern (left) and summer flounder (right) both spend much of their early lives over shallow estuarine and coastal bottoms before mature fish move offshore to spawn. | Image credits: J. Weferling, iNaturalist (left); harrier, iNaturalist (right)

    Southern flounder (Paralichthys lethostigma) spend the first years of their lives inside estuaries, lying over mud, sand, oyster habitat, creek bottoms, and other shallow nursery and feeding areas where they prey on fish and crustaceans. In North Carolina, many females begin reaching reproductive maturity around ages one to two and roughly 16 inches in length, although growth and maturity vary considerably among individual fish (Midway & Scharf, 2012).
    That means a southern flounder can spend years growing within the estuary before ever contributing to the offshore spawning population. Immature fish may remain within estuarine waters through winter, while mature fish begin leaving in fall for offshore spawning habitat. Fish encountered farther offshore tend to be larger and older, while younger fish remain more closely associated with the sounds, rivers, and creeks where they grew (Craig et al., 2015).
    A fish that spent its first years nearly invisible beneath New River mud can suddenly become part of an offshore migration.

    Summer flounder (Paralichthys dentatus) make a similar outward journey, although their early life follows a slightly different timetable. Larvae and juveniles use coastal bays, sounds, and estuaries as nursery habitat for roughly their first 18 to 20 months, and most reach reproductive maturity around age two to three. In the South Atlantic Bight, about half are mature by roughly 11 to 12 inches total length, although females generally mature at a somewhat larger size than males (Packer, 1999).

    Like southern flounder, they spend their younger years feeding and growing in protected coastal habitat before mature fish begin moving offshore in fall toward continental-shelf spawning grounds. By then, the fish leaving the estuary are not simply larger versions of the juveniles that remain behind; they are the part of the population capable of producing the next generation.
    So the two flatfish a beachgoer might easily confuse are doing something remarkably similar at this time of year. Both spend their younger years in shallow coastal and estuarine nursery habitat, and both eventually move offshore to spawn. What differs is the timing—how quickly they mature, how long they remain closely tied to those nursery grounds, and where along the coast each species is most concentrated.

    The Fall Runs Gather Nearshore

    The familiar fishes around piers change with fall too.

    Spot (Leiostomus xanthurus) and Atlantic croaker (Micropogonias undulatus) spend important parts of their early lives inside estuaries, feeding over sandy and muddy bottoms on worms, small crustaceans, organic material, and other small prey (Warlen & Burke, 1990; Ross, 1988)

    Atlantic croaker (Micropogonias undulatus) and spot (Leiostomus xanthurus), two familiar estuarine fishes that move toward coastal spawning waters in fall.  | Image credit: C. Dzbanski
    Atlantic croaker (Micropogonias undulatus) and spot (Leiostomus xanthurus), two familiar estuarine fishes that move toward coastal spawning waters in fall. | Image credit: C. Dzbanski

    Spot remain closely tied to estuarine nursery habitat through their first year, gradually moving into deeper and saltier parts of the system as they grow. By fall, the larger fish begin gathering closer to channels, inlets, and the ocean before continuing toward offshore spawning grounds south of Cape Hatteras. There, spawning continues through fall and winter in substantially warmer shelf water, roughly 63–77°F, with the strongest activity around 68°F (Warlen & Chester, 1985; Allen et al., 2024).

    Atlantic croaker follow a similar route on a slightly different schedule. Young croaker enter low-salinity estuarine nursery areas after being spawned offshore, then grow rapidly through their first year. As fall develops, many begin moving back toward open coastal water, with the spawning migration beginning as early as September and continuing into winter (White & Chittenden, 1977; Norcross & Austin, 1988).

    Weakfish (Cynoscion regalis) join that same seasonal pull toward the coast. Through spring and summer they use sounds, estuaries, and nearshore habitat, feeding heavily on shrimp, crustaceans, and smaller fishes. As autumn water cools toward about 75°F, they begin gathering and shifting offshore and south; during warmer years, some linger longer before making that move (Krause et al., 2020).

    Weakfish (Cynoscion regalis), a fall migrant along the Atlantic coast and currently listed as Endangered on the IUCN Red List. | Image credit: aiden007, iNaturalist
    Weakfish (Cynoscion regalis), a fall migrant along the Atlantic coast and currently listed as Endangered on the IUCN Red List. | Image credit: aiden007, iNaturalist

    By this point in fall, fishes that spent summer scattered through different parts of the estuary are beginning to converge along the same channels, inlets, and nearshore corridor. The movement is outward, but not entirely.

    While larger spot and croaker are leaving for offshore spawning grounds, their next generation is already beginning the opposite journey. Larvae produced offshore in fall and winter can begin entering North Carolina estuaries by late fall and early winter, with that inward movement continuing through spring (Warlen & Burke, 1990; Allen et al., 2024).

    So even as one generation moves out through the inlet, another is beginning to come back in.

    The Fish That Stay—but Change Address

    Migration does not always mean leaving Onslow County. For some fishes, fall means finding a different part of the same estuary.

    Spotted seatrout (Cynoscion nebulosus), or speckled trout, remain in coastal North Carolina through winter, but they do not necessarily stay where they spent August. As the shallow sounds and creek edges cool, trout begin gathering around channels, deeper holes, creek mouths, and other places where a few extra feet of water can provide more stable temperatures.

    Spotted seatrout (Cynoscion nebulosus) moving through shallow coastal water before shifting toward deeper winter habitat as temperatures fall. | Image credit: charliew82, iNaturalist
    Spotted seatrout (Cynoscion nebulosus) moving through shallow coastal water before shifting toward deeper winter habitat as temperatures fall. | Image credit: charliew82, iNaturalist

    That difference becomes increasingly important as winter approaches. Spotted seatrout begin showing cold stress when water falls below about 45°F, and prolonged periods below roughly 44.6°F can produce substantial winter mortality in North Carolina. Deeper sections of an estuary can remain slightly warmer during a severe cold event, giving fish somewhere to retreat when the shallows become too cold (Ellis, Buckel, & Hightower, 2017; Ellis, Buckel, Hightower, & Poland, 2017).

    So the autumn congregation of trout around creek mouths, bridge structure, channels, and deep holes is more than a change in where they happen to be feeding. By fall, they are beginning to settle into the parts of the estuary that may carry them through winter.

    Black drum (Pogonias cromis) reorganize themselves through fall as well, although their movement depends partly on age. Young black drum spend their first year within estuaries, feeding over mud, sand, oyster habitat, and other bottoms rich in worms, small crustaceans, and mollusks. As they grow, they begin using saltier water and deeper coastal habitat, while larger fish are often associated with oyster bars, bridge and dock pilings, channels, and other structure where clams, oysters, crabs, and other bottom prey collect (North Carolina Division of Marine Fisheries, 2026).

    Black drum (Pogonias cromis) use estuaries when young, then shift toward deeper, saltier water as they grow and fall progresses. | Image credit: zachs, iNaturalist
    Black drum (Pogonias cromis) use estuaries when young, then shift toward deeper, saltier water as they grow and fall progresses. | Image credit: zachs, iNaturalist

    By late fall, black drum generally shift away from the shallowest summer habitat toward deeper bays, sounds, channels, and offshore water. Unlike spotted seatrout, there is not one well-defined temperature at which that movement begins. Instead, cooling water gradually changes where suitable feeding and winter habitat remain available, with older fish tending to range farther toward high-salinity and offshore waters (North Carolina Division of Marine Fisheries, 2026).

    A piling or oyster bar that held one mix of fishes through summer may still be occupied in November, but by a different combination of animals using the same structure for colder-water feeding and refuge.

    The habitat has not disappeared. Its seasonal community has changed.

    Shrimp Begin Pouring Out of the Creeks

    Some of the most important migrants along the Onslow County coast are only a few inches long.

    White shrimp (Litopenaeus setiferus), locally called greentails, spend much of their early lives inside estuarine nursery habitat. They grow rapidly in warm water, and once they reach only about 0.8 to 1.2 inches long, they begin leaving the shallowest marsh habitat for deeper creeks, rivers, bays, and sounds. By late summer and fall, larger young shrimp—often around 4.7 inches or more—are moving farther downstream toward channels, inlets, and ultimately the ocean (North Carolina Division of Marine Fisheries, 2023).

    White shrimp (Litopenaeus setiferus) grow quickly in estuarine nurseries before moving downstream toward sounds, inlets, and coastal water in late summer and fall. | Image credit: portulaca, iNaturalist
    White shrimp (Litopenaeus setiferus) grow quickly in estuarine nurseries before moving downstream toward sounds, inlets, and coastal water in late summer and fall. | Image credit: portulaca, iNaturalist

    Cooling water helps drive that progression, but rainfall can accelerate it. Heavy freshwater input lowers estuarine salinity and can push shrimp downstream and toward the ocean before they otherwise would have left. That means a wet fall and a dry fall do not necessarily produce the same migration (North Carolina Division of Marine Fisheries, 2023).

    The shrimp are responding to an estuary that is changing around them, and almost everything seems interested in eating them. Flounder, speckled trout, red drum, weakfish, sharks, wading birds, and humans all take advantage of shrimp as they move through the coastal food web (North Carolina Division of Marine Fisheries, 2023).

    A strong outward movement of white shrimp is therefore not merely a shrimp migration. It is a moving food resource.

    When those shrimp leave marsh creeks and spread toward the sound and inlet, predators that were previously separated begin encountering the same pulse of prey in increasingly narrow parts of the estuary.

    The estuary briefly becomes a funnel.

    The Blue Crabs Take Different Roads

    Blue crabs (Callinectes sapidus) complicate the idea of a single fall migration even further because males and females do not necessarily go the same direction.

    Blue crab (Callinectes sapidus) in shallow estuarine habitat; mature females eventually move toward saltier water and coastal spawning areas. | Image credit: lenora_irene, iNaturalist
    Blue crab (Callinectes sapidus) in shallow estuarine habitat; mature females eventually move toward saltier water and coastal spawning areas. | Image credit: lenora_irene, iNaturalist

    Adult males generally remain farther upriver in lower-salinity water, while mature females move toward saltier portions of the estuary and eventually toward inlet and coastal spawning habitat. Females can travel considerable distances during this migration, using salinity gradients, tides, and currents to move toward the high-salinity water needed for spawning (Bell & Eggleston, 2023; Forward et al., 2003).

    That split makes sense once their life cycle is considered. Females typically mate in brackish estuarine water, then store sperm until they are ready to produce an egg mass. As spawning approaches, they move toward the lower estuary and inlet, where much saltier water provides the conditions their developing larvae need. Eggs hatch near the mouth of the estuary or just beyond it, and the larvae are carried offshore before later returning toward the coast as postlarvae (Forward et al., 2003; Epifanio, 2019).

    The same inlet therefore serves two directions of the blue crab life cycle: mature females move outward toward spawning water, while a later generation is carried back toward estuarine nursery habitat.

    For a blue crab, the difference between a brackish river and a salty inlet is not simply scenery. One supports mating and much of adult life, while the other provides the salinity needed to begin the next generation.

    A single life cycle requires both.

    Rays Begin Leaving the Shallows

    Large dark wings moving beneath clear water are among the more obvious signs that rays are using shallow coastal habitat during summer. By fall, where those rays appear—and how they move through the coast—begins to change.

    Cownose rays (Rhinoptera bonasus) are highly mobile schooling rays that use North Carolina sounds, estuaries, and nearshore waters during the warmer months. Through summer they may be scattered across that habitat, sometimes appearing alone or in small groups over shallow flats and sounds. As fall develops, rays that have been using North Carolina estuaries begin moving toward the ocean side, while migrants arriving from farther north join the same southbound corridor along the Carolina coast.

    That is when larger schools can become more noticeable along the beaches and nearshore waters. Their movement continues south toward winter habitat off Florida, with cooling water helping shape when they leave northern and estuarine habitats (Goodman et al., 2010; Omori & Fisher, 2017; Bangley et al., 2021).

    Cownose rays (Rhinoptera bonasus) traveling in a school, a familiar sight as they gather and move along the coast in fall. | Image credit: Chesapeake Bay Program
    Cownose rays (Rhinoptera bonasus) traveling in a school, a familiar sight as they gather and move along the coast in fall. | Image credit: Chesapeake Bay Program

    For someone watching from Topsail, the rays seen scattered through the sound during summer can become part of something much larger by fall. A few dark wings moving over an estuarine flat may give way to schools traveling along the ocean side as North Carolina becomes part of the passage between northern summer waters and winter habitat farther south.

    Southern stingrays (Hypanus americanus) make a quieter seasonal shift. Their summer presence along North Carolina is part of a much older warm-season pattern, with southern stingrays historically documented moving north along the Carolina coast as warmer water expands their usable habitat (Coles, 1913).

    Southern stingray (Hypanus americanus) resting on the seafloor, where this bottom-oriented ray remains closely tied to benthic habitat even as it shifts seasonally. | Image credit: © Steve M. Schelb
    Southern stingray (Hypanus americanus) resting on the seafloor, where this bottom-oriented ray remains closely tied to benthic habitat even as it shifts seasonally. | Image credit: © Steve M. Schelb

    Unlike cownose rays traveling in schools higher in the water column, southern stingrays remain closely tied to the bottom. Through summer, they can be a familiar sight moving over warm sand and mud flats, along creek mouths, and through shallow estuarine water as they search the bottom for worms, bivalves, shrimp, crabs, and small fishes. Even when they move between habitats, much of that movement remains along or just above the benthic surface rather than through open water (Gilliam & Sullivan, 1993; Tilley et al., 2013).

    As the shallow flats cool through fall, they become less common in the places where beachgoers may have seen them repeatedly through July and August. Their seasonal movement is not mapped nearly as clearly in North Carolina as that of cownose rays, so we cannot point to one temperature or one offshore route. What we can say is that southern stingrays are capable of moving between shallow flats and considerably deeper bottom habitat while remaining closely associated with the seafloor (Coles, 1913; Corcoran et al., 2013).

    For someone watching the shallows, that change may simply look like absence. The stingray that repeatedly crossed the same warm flat all summer is suddenly harder to find—not because it has joined a large southbound school above the bottom, but because its usable benthic habitat has shifted beyond the shallows where it was easiest to see.

    Red Drum Gather at the Edges

    Red drum (Sciaenops ocellatus), and our state fish, add another layer to the fall movement. Young fish spend their first years closely tied to estuaries, growing quickly from roughly 12 to 14 inches by their first birthday to more than 27 inches during their second full year. They do not reach reproductive maturity quite as quickly, however. In North Carolina, most become mature around ages three to four, when they are roughly 30 to 36 inches long (Ross et al., 1995).

    Red drum (Sciaenops ocellatus) grow in estuaries when young, while larger adults gather around inlets and nearshore waters during late-summer and fall spawning. | Image credit: colesutton, iNaturalist
    Red drum (Sciaenops ocellatus) grow in estuaries when young, while larger adults gather around inlets and nearshore waters during late-summer and fall spawning. | Image credit: colesutton, iNaturalist

    That difference is something a beachgoer or angler can actually see. The smaller “puppy drum” encountered along marsh edges, creeks, and sounds are still growing within the estuarine part of their life cycle, while the much larger fish appearing around beaches and inlets are increasingly part of the adult population that spends more time in coastal and ocean waters.
    By late summer and early fall, mature red drum gather around inlets, beaches, and nearshore waters, where spawning and feeding can overlap. In North Carolina, spawning occurs from August into early October near barrier-island inlets and adjacent coastal waters. During that same period, adults move more actively between estuarine and ocean habitats (Ross et al., 1995; Bacheler et al., 2009).

    That puts a large red drum outside New River Inlet directly into the same corridor carrying mullet, menhaden, shrimp, spot, croaker, and other prey toward the ocean. It may be there to spawn, to feed, or simply because its own seasonal movement has brought it into the same narrow stretch of coast.

    As fall gives way to winter, mature adults increasingly move into ocean waters where temperatures remain more moderate, while younger red drum are much more likely to remain behind in the estuary (Stewart & Scharf, 2008).

    The Offshore Visitors Come Close

    Fall also brings some animals toward the coast before eventually carrying them away.

    King mackerel (Scomberomorus cavalla) are warm-water fish that seldom move into water much below about 68°F. Through summer and the warmer part of fall, they can move surprisingly close to the beaches, inlet mouths, and nearshore reefs of North Carolina, following schools of menhaden, mullet, sardines, and other prey into places where a beachgoer or pier angler may suddenly encounter a fish that spends much of its time farther offshore (North Carolina Division of Marine Fisheries, 2022).

    That window does not last. As coastal water continues cooling toward the lower edge of their preferred range, king mackerel begin shifting south and farther toward the warmer waters of the continental shelf. By winter, much of the Atlantic population has moved toward southern Florida, while some fish remain in deeper North Carolina waters near the Gulf Stream (North Carolina Division of Marine Fisheries, 2022).

    For a few weeks, that creates an unusual overlap along the Onslow coast. Animals moving out of the estuary meet predators moving closer to shore to feed, while other migrants are already passing south or beginning their move offshore. An inlet or artificial reef that seemed relatively quiet several weeks earlier can suddenly sit at the crossing point of several different seasonal routes.

    For a short time, it becomes an intersection.

    Then the Menhaden Arrive

    By October and November, another migration becomes increasingly visible.

    Atlantic menhaden (Brevoortia tyrannus) move south along the Atlantic coast as fall deepens, with older and larger fish returning from summer waters farther north. Spawning can occur along the migration route from late fall into early spring, but one of the major winter gathering areas lies off North Carolina near Cape Hatteras (Lewis et al., 1987; Nicholson, 1978).

    For Onslow County, that means some of the dark schools appearing beyond the breakers are part of a much larger coastwide movement passing our beaches on the way toward winter spawning waters.

    Menhaden occupy an unusual place in the coastal food web. They filter tiny phytoplankton and zooplankton from the water, then gather that scattered production into dense schools of oily fish large enough for predators to chase (Lewis & Peters, 1994). Bluefish, striped bass, sharks, tunas, dolphins, and seabirds all take advantage of them, making menhaden one of the connections between plankton near the bottom of the food web and some of the largest predators along the coast (Chagaris et al., 2020; Lewis & Peters, 1994).

    For a beachgoer, the first sign may simply be a dark patch offshore that does not move like a shadow. Then birds begin gathering above it. The surface breaks as predators push into the school from below, and what looked like an indistinct patch of water suddenly becomes one of the busiest places along the beach.

    That is when looking up becomes as important as looking into the water.

    Because another migration has arrived.

    The Atlantic Flyway Meets the Fall Fish Run

    The Atlantic Flyway follows the eastern edge of North America, placing the North Carolina coast directly beneath one of the continent’s major migration routes. For birds traveling hundreds or thousands of miles between breeding and wintering grounds, Onslow County is not simply coastline passing beneath their wings. Its beaches, marshes, tidal flats, sounds, and inlets can provide places to rest and replenish the energy needed for the next part of the journey (Smith et al., 2022).

    The Atlantic Flyway follows the eastern edge of North America, carrying migrating birds directly along the North Carolina coast. | Image credit: Audubon
    The Atlantic Flyway follows the eastern edge of North America, carrying migrating birds directly along the North Carolina coast. | Image credit: Audubon

    Fall makes that stop especially busy because the migration overhead is unfolding at the same time the water below is changing. Shrimp are moving out of creeks. Mullet and other fishes are funneling toward the inlets. Schools of bait gather along the beaches, and menhaden begin moving down the coast. For birds that feed on fishes and coastal invertebrates, those movements can turn the Onslow shoreline into a series of feeding opportunities along the Atlantic Flyway.

    But the transition is not a clean exchange in which the summer birds simply leave and winter birds immediately take their places. It happens gradually, with departures, arrivals, and birds merely passing through overlapping for weeks.

    The Birds Moving Through or South

    Some of the first changes are easiest to notice in the marsh. Green herons (Butorides virescens) begin moving south from late August through October, while least bitterns (Ixobrychus exilis) also leave much of their northern breeding range for warmer winter habitat. A bird that spent summer hunting from the edge of a tidal creek may simply become harder to find as September advances (Smith et al., 2022).

    Along the beaches and nesting islands, the summer community begins loosening in several directions at once. Wilson’s plovers (Anarhynchus wilsonia), least terns (Sternula antillarum), gull-billed terns (Gelochelidon nilotica), black skimmers (Rynchops niger), and sandwich terns (Thalasseus sandvicensis) begin leaving breeding areas or redistributing south along the coast. Royal terns (Thalasseus maximus) may linger longer, while ospreys (Pandion haliaetus) begin following waterways and coastlines toward wintering grounds farther south (North Carolina Wildlife Resources Commission, 2025; Smith et al., 2022).

    The shorebirds make the transition even less tidy.

    The eastern Willet (Tringa semipalmata semipalmata) breeds in Atlantic salt marshes, including those along the North Carolina coast, before leaving for wintering grounds that can lie as far away as northern South America. But the Willet standing on a Topsail flat in fall is not automatically one of the birds that nested here. Western Willets (Tringa semipalmata inornata), which breed in the interior of western North America, can also occur along the Atlantic coast outside the breeding season. For a few weeks, birds from very different summer landscapes may use the same Carolina shoreline (Oswald et al., 2016; Huysman et al., 2022).

    Lesser yellowlegs (Tringa flavipes) and greater yellowlegs (Tringa melanoleuca) add another layer of passing traffic. They arrive from breeding grounds much farther north, with adults beginning their southward movements as early as July and younger birds following later. Along coastal North Carolina, exposed flats, shallow marsh edges, and pools of tidal water become temporary feeding grounds along that journey (Smith et al., 2022).

    That makes the falling tide part of the migration too. A mudflat that looked empty beneath the previous high tide can suddenly hold Willets, yellowlegs, plovers, and other shorebirds probing exposed sediment for worms, small crustaceans, mollusks, and other prey. North Carolina barrier-island studies have found fall shorebirds shifting among the swash zone, wet sand, spits, and tidal habitat as water levels change, using different pieces of the shoreline for feeding and resting through the tidal cycle (Tarr, 2008).

    For some of those birds, the stop may last days. For others, only hours. The tide falls, a feeding ground appears, and birds moving along the Atlantic coast briefly settle into it before the water—or the migration—carries them onward.

    The Winter Coast Begins Arriving

    The winter coast does not arrive all at once. Its first birds begin appearing in September, more follow through October, and by November the sounds, marshes, and beaches of Onslow County can hold a noticeably different community than they did at the end of summer.

    On the sounds and protected water behind the barrier islands, buffleheads (Bucephala albeola) begin settling into sheltered coves, bays, and estuaries, repeatedly disappearing beneath the surface in search of small crustaceans, mollusks, and other aquatic prey. Red-breasted mergansers (Mergus serrator) arrive as well, often working shallow coastal water and estuaries in small groups as they dive after fish (Gauthier, 1993; Titman, 1999; Smith et al., 2022).

    The marsh begins changing at the same time. American black ducks (Anas rubripes) appear more regularly in salt marshes, tidal creeks, ponds, and estuaries, while Green-winged teal (Anas crecca) increase in shallow protected water. Both spent the breeding season much farther north, but by fall the sounds and marshes of the Atlantic coast have become part of their winter landscape (Robinson et al., 2016; Smith et al., 2022).

    Along the ocean side, the change is visible at the water’s edge. Dunlin (Calidris alpina), sanderlings (Calidris alba), red knots (Calidris canutus), and black-bellied plovers (Pluvialis squatarola) begin working beaches, shoals, exposed flats, and inlet margins. Some will remain along the southeastern coast through winter, while others are pausing only long enough to feed before continuing south. As the tide falls they spread across wet sand and exposed flats; when the water returns, they are gradually pushed toward higher beaches and roosting areas (Burger et al., 2012; Smith et al., 2022; Tarr, 2008).

    Red knots make the scale of that movement especially clear. A bird standing quietly near the wrack line may have arrived from Arctic breeding grounds and may still be headed toward winter habitat in the southeastern United States, the Caribbean, or northern South America. Individual birds do not all travel the same route or distance, but for some, the Carolina coast is only one stop in a journey spanning thousands of miles (Burger et al., 2012; Smith et al., 2022).

    That changes what a quiet fall beach can mean. The wet sand, tidal flats, wrack, marshes, and sheltered water are not empty spaces between destinations. For birds arriving from the north, they are places to replace the energy already spent before the next part of the migration begins.

    When the Food Web Takes to the Air

    Fall adds another layer of hunters above the shoreline.

    Peregrine falcons (Falco peregrinus) move south along the Atlantic coast during migration, often following the same barrier islands, mudflats, and shorelines being used by migrating shorebirds. They are not interested in the mullet, shrimp, or menhaden moving below the surface. They are interested in the birds feeding around them. Shorebirds, ducks, gulls, and other coastal birds become prey themselves, adding another level to the food web moving through the coast (Smith et al., 2022).

    Farther offshore, the change becomes visible in a different way. Double-crested cormorants (Nannopterum auritum) arrive along the Carolina coast in large numbers and spend much of their time diving after fish. Menhaden are among the schooling fishes they readily take, tying these winter visitors directly into the same fall movement already passing through the inlets and along the beaches (Watts et al., 2023).

    Red-throated loons (Gavia stellata) and common loons (Gavia immer) begin appearing along the ocean side as well. Both spend the warmer months much farther north, but by late fall they are back in shallow marine waters, sounds, bays, and estuaries where fish are abundant. A bird that spent summer on a northern lake or tundra pond may now be diving just beyond the breakers along Topsail (Stenhouse et al., 2020; Smith et al., 2022).

    Then come the northern gannets (Morus bassanus).

    By late fall, they become one of the most spectacular signs that the seasonal food web has shifted. Northern gannets spend much of the nonbreeding season between New York and North Carolina, feeding almost entirely on schooling fishes such as herring, mackerel, and menhaden over the continental shelf (Mowbray, 2020; Smith et al., 2022).

    From shore, a feeding aggregation can seem to appear from nowhere. Large white birds circle above a patch of ocean, fold their wings, and plunge headfirst into the water. One follows another until dozens may be dropping into the same moving patch of sea.

    The important thing may not be the gannets themselves, but what they are pointing toward.
    Beneath them is a school of fish. Around that school may be bluefish, sharks, dolphins, or other large predators pushing the same prey toward the surface. The birds above and the predators below are using the same concentration of food from opposite directions.

    What began months earlier as plankton, marsh production, and small animals feeding inside estuaries has now moved far enough through the food web to become visible from the beach as birds falling out of the sky.

    What Happens if One Migration Does Not Arrive?

    It is easy to think about migration as something belonging to individual species—the mullet run, the shrimp migration, the shark migration, the Atlantic Flyway. But the coast does not experience those movements separately. Predators are responding to prey, young fishes are entering estuaries when nursery habitat and food are available, adults are leaving when spawning habitat lies offshore, and blue crabs are moving between different salinity zones because different stages of their lives depend on different parts of the estuary (Warlen & Burke, 1990; Forward et al., 2003).

    That means a change in one migration does not necessarily stop with the animal making it.

    If fewer mullet leave an estuary, there may be less concentrated prey moving along the beach for bluefish, sharks, pelicans, and terns. The difference is not simply fewer mullet in one place. Some of the energy that spent summer accumulating inside the estuary now reaches the nearshore food web in a different amount, at a different time, or along a different route (Bacheler et al., 2005).

    White shrimp show how quickly those relationships can shift. Heavy rainfall lowers estuarine salinity and can push shrimp toward the inlet earlier than they might have moved during a drier fall. Predators farther inside the estuary may encounter fewer shrimp, while those gathered nearer the inlet may suddenly encounter more. The migration still happens, but its timing changes where that pulse of food becomes available (North Carolina Division of Marine Fisheries, 2023).

    Temperature can alter the overlap in another way. A coastal shark that remains farther north later into a warm fall may not encounter its prey in quite the same places or at quite the same time if those prey are responding to a different set of seasonal cues. Warmer ocean conditions are already capable of delaying southward shark migrations and extending how long some species remain in northern seasonal habitat (Manz et al., 2025).

    None of this means every migration must occur on the same date each year. Coastal systems have always varied with storms, rainfall, temperature, currents, and food availability. What matters is that the movements continue to cross one another often enough for the relationships among them to persist.

    A predator still has to encounter its prey. A larva still has to reach suitable nursery habitat, and a migrating bird still has to find enough food to continue south.

    The timing does not have to be exact, but the meeting still has to happen.

    Watching the Coast Change

    By September, the first changes are already beginning. Mullet gather near the inlets, shrimp move out of tidal creeks, rays become less common over shallow flats, and feeding birds begin revealing where bait has collected near the surface.

    By October and November, the same places can hold a very different community. Some animals have moved only a few miles into deeper water, while others are passing Onslow County on journeys that continue far beyond the Carolina coast.

    The landscape itself looks much the same. New River Inlet still cuts through the barrier island. The marsh grass still bends with the wind. The same beach stretches north and south.
    What changes is who is moving through it.

    For a few months each fall, Onslow County becomes a meeting place between departures, arrivals, and animals simply shifting into the next piece of habitat they need.

    The landscape stays where it is.
    The food web moves through it.

    Wilson Bay along the New River in Jacksonville, North Carolina. The landscape stays where it is, even as the food web moves through it. | Image credit: A. Mitchell
    Wilson Bay along the New River in Jacksonville, North Carolina. The landscape stays where it is, even as the food web moves through it. | Image credit: A. Mitchell

    References

    Allen, D. M., Govoni, J. J., Able, K. W., Buckel, J. A., Hale, E. A., Hilton, E. J., Kellison, G. T., Targett, T. E., Taylor, J. C., & Walsh, H. J. (2024). Long-term dynamics of larval and early juvenile spot (Leiostomus xanthurus) off the U.S. East Coast: Relating ocean origins, estuarine Ingress, and changing environmental conditions. Fishery Bulletin, 122(4), 162-185. https://doi.org/10.7755/fb.122.4.3

    Bacheler, N. M., Paramore, L. M., Burdick, S. M., Buckel, J. A., & Hightower, J. E. (2009). Variation in movement patterns of red drum (Sciaenops ocellatus) inferred from conventional tagging and ultrasonic telemetry. Fishery Bulletin, 107(4), 405-419. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/2009/1074/bacheler.pdf

    Bacheler, N. M., Wong, R. A., & Buckel, J. A. (2005). Movements and mortality rates of striped mullet in North Carolina. North American Journal of Fisheries Management, 25(1), 361-373. https://doi.org/10.1577/m04-033.1

    Bangley, C. (2026, July 9). Sharks of North Carolina. Coastwatch. https://ncseagrant.ncsu.edu/coastwatch/sharks-of-north-carolina/

    Bangley, C. W., Edwards, M. L., Mueller, C., Fisher, R. A., Aguilar, R., Heggie, K., Richie, K., Ahr, B. J., & Ogburn, M. B. (2021). Environmental associations of cownose ray (Rhinoptera bonasus) seasonal presence along the U.S. Atlantic coast. Ecosphere, 12(9). https://doi.org/10.1002/ecs2.3743

    Bell, G. W., & Eggleston, D. B. (2023). Timing and route of migration of mature female blue crabs in a large, wind-driven Estuary. Transactions of the American Fisheries Society, 152(2), 253-269. https://doi.org/10.1002/tafs.10391

    Bethea, D. M., Carlson, J. K., & Buckel, J. A. (2006). Ontogenetic and site-related trends in the diet of the Atlantic sharpnose shark Rhizoprionodon terraenovae from the northeast Gulf of Mexico. Bulletin of Marine Science, 78(2), 287-307. https://www.ingentaconnect.com/content/umrsmas/bullmar/2006/00000078/00000002/art00005?crawler=true

    Bichy, J. B. (2004). A life history assessment on the reproduction and growth of striped mullet, Mugil cephalus, in North Carolina [Unpublished master’s thesis]. North Carolina State University.

    Burger, J., Niles, L. J., Porter, R. R., Dey, A. D., Koch, S., & Gordon, C. (2012). Using a shore bird (red knot) fitted with geolocators to evaluate a conceptual risk model focusing on offshore wind. Renewable Energy, 43, 370-377. https://doi.org/10.1016/j.renene.2011.11.006

    Carlson, J. K., Sulikowski, J. R., & Baremore, I. E. (2006). Do differences in life history exist for blacktip sharks, Carcharhinus limbatus, from the United States south Atlantic bight and eastern Gulf of Mexico? Environmental Biology of Fishes, 77(3-4), 279-292. https://doi.org/10.1007/s10641-006-9129-x

    Chagaris, D., Drew, K., Schueller, A., Cieri, M., Brito, J., & Buchheister, A. (2020). Ecological reference points for Atlantic menhaden established using an ecosystem model of intermediate complexity. Frontiers in Marine Science, 7. https://doi.org/10.3389/fmars.2020.606417

    Coles, R. J. (1913). Notes on the embryos of several species of rays, with remarks on the northward summer migration of certain tropical forms observed on the coast of North Carolina. Bulletin of the American Museum of Natural History, 32, 29-35. https://www.biodiversitylibrary.org/page/26891225#page/491/mode/1up

    Corcoran, M. J., Wetherbee, B. M., Shivji, M. S., Potenski, M. D., Chapman, D. D., & Harvey, G. M. (2013). Supplemental feeding for ecotourism reverses Diel activity and alters movement patterns and spatial distribution of the southern Stingray, Dasyatis americana. PLoS ONE, 8(3), e59235. https://doi.org/10.1371/journal.pone.0059235

    Craig, J. K., Smith, W. E., Scharf, F. S., & Monaghan, J. P. (2015). Estuarine residency and migration of southern flounder inferred from conventional tag returns at multiple spatial scales. Marine and Coastal Fisheries, 7(1), 450-463. https://doi.org/10.1080/19425120.2015.1079578

    Ellis, T. A., Buckel, J. A., Hightower, J. E., & Poland, S. J. (2017). Relating cold tolerance to winterkill for spotted seatrout at its northern latitudinal limits. Journal of Experimental Marine Biology and Ecology, 490, 42-51. https://doi.org/10.1016/j.jembe.2017.01.010

    Ellis, T., Buckel, J., & Hightower, J. (2017). Winter severity influences spotted seatrout mortality in a southeast US estuarine system. Marine Ecology Progress Series, 564, 145-161. https://doi.org/10.3354/meps11985

    Epifanio, C. E. (2019). Early life history of the blue crab Callinectes sapidus: A review. Journal of Shellfish Research, 38(1), 1-22. https://doi.org/10.2983/035.038.0101

    Forward, R. B., Tankersley, R. A., & Welch, J. M. (2003). Selective tidal-stream transport of the blue crab Callinectes sapidus: An overview. Bulletin of Marine Science, 72(2), 347-365. https://scholars.duke.edu/publication/771475

    Gauthier, G. (1993). Bufflehead (Bucephala albeola). In The Birds of North America (67th ed.). The Academy of Natural Sciences of Philadelphia & The American Ornithologists’ Union.

    Gilliam, D. S., & Sullivan, K. M. (1993). Diet and feeding habits of the southern stingray Dasyatis americana in the central Bahamas. Bulletin of Marine Science, 52(3), 1007-1013. https://nsuworks.nova.edu/cgi/viewcontent.cgi?article=1570&context=occ_facarticles

    Goodman, M. A., Conn, P. B., & Fitzpatrick, E. (2010). Seasonal occurrence of Cownose rays (Rhinoptera bonasus) in North Carolina’s estuarine and coastal waters. Estuaries and Coasts, 34(3), 640-651. https://doi.org/10.1007/s12237-010-9355-5

    Heupel, M., Carlson, J., & Simpfendorfer, C. (2007). Shark nursery areas: Concepts, definition, characterization and assumptions. Marine Ecology Progress Series, 337, 287-297. https://doi.org/10.3354/meps337287

    Huysman, A. E., Cooper, N. W., Smith, J. A., Haig, S. M., Heath, S. A., Johnson, L., Olson, E., Regan, K., Wilson, J. K., & Marra, P. P. (2022). Strong migratory connectivity indicates Willets need subspecies-specific conservation strategies. Ornithological Applications, 124(3). https://doi.org/10.1093/ornithapp/duac015

    Jensen, D. R., & Graves, J. E. (2020). Movements, habitat utilization, and post-release survival of cobia (Rachycentron canadum) that summer in Virginia waters assessed using pop-up satellite archival tags. Animal Biotelemetry, 8(1). https://doi.org/10.1186/s40317-020-00212-0

    Kohler, N. E., Casey, J. G., & Turner, P. A. (1998). NMFS Cooperative Shark Tagging Program, 1962–93: An atlas of shark tag and recapture data. Marine Fisheries Review, 60(2), 1-87. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/mfr6021.pdf

    Krause, J. R., Hightower, J. E., Buckel, J. A., Turnure, J. T., Grothues, T. M., Manderson, J. P., Rosendale, J. E., & Pessutti, J. P. (2020). Using acoustic telemetry to estimate weakfish survival rates along the U.S. East Coast. Marine and Coastal Fisheries, 12(5), 241-257. https://doi.org/10.1002/mcf2.10095

    Lewis, R. M., Ahrenholz, D. W., & Epperly, S. P. (1987). Fecundity of Atlantic menhaden, Brevoortia tyrannus. Estuaries, 10(4), 347. https://doi.org/10.2307/1351894

    Lewis, V. P., & Peters, D. S. (1994). Diet of juvenile and adult Atlantic menhaden in estuarine and coastal habitats. Transactions of the American Fisheries Society, 123(5), 803-810. https://doi.org/10.1577/1548-8659(1994)123<0803:dojaaa>2.3.co;2

    Lund, W. A., & Maltezos, G. C. (1970). Movements and migrations of the bluefish, Pomatomus saltatrix, tagged in waters of New York and southern New England. Transactions of the American Fisheries Society, 99(4), 719-725. https://doi.org/10.1577/1548-8659(1970)99<719:mamotb>2.0.co;2

    Manz, M. H., Shipley, O. N., Cerrato, R. M., Hueter, R. E., Newton, A. L., Tyminski, J. P., Franks, B. R., Curtis, T. H., Fischer, C., Zacharias, J. P., Scott, C., Dunton, K. J., Kneebone, J., Peterson, B. J., Scannell, B. J., Dodd, J. F., & Frisk, M. G. (2025). Predictions of southern migration timing in coastal sharks under future ocean warming. Conservation Biology, 39(6), e70080. https://doi.org/10.1111/cobi.70080

    McCandless, C. T., Pratt, Jr., H. L., Kohler, N. E., Merson, R. R., & Recksiek, C. W. (2007). Distribution, localized abundance, movements, and migrations of juvenile sandbar sharks tagged in Delaware Bay. In Shark nursery grounds of the Gulf of Mexico and the east coast waters of the United States (pp. 45-62). American Fisheries Society Symposium. https://doi.org/10.47886/9781888569810.ch4

    Merson, R. R., & Pratt, Jr., H. L. (2001). Distribution, Movements and Growth of Young Sandbar Sharks, Carcharhinus Plumbeus, in the Nursery Grounds of Delaware Bay. Environmental Biology of Fishes, 61, 13-24. https://link.springer.com/article/10.1023/A:1011017109776

    Midway, S. R., & Scharf, F. S. (2012). Histological analysis reveals larger size at maturity for southern flounder with implications for biological reference points. Marine and Coastal Fisheries, 4(1), 628-638. https://doi.org/10.1080/19425120.2012.717524

    Mowbray, T. B. (2020). Northern Gannet (Morus bassanus). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology. https://doi.org/10.2173/bow.norgan.01

    Nicholson, W. R. (1978). Movements and population structure of Atlantic menhaden indicated by tag returns. Estuaries, 1(3), 141. https://doi.org/10.2307/1351455

    NOAA Fisheries. (2017). Final Amendment 10 to the 2006 consolidated Atlantic highly migratory species fishery management plan: Essential fish habitat and environmental assessment. https://www.habitat.noaa.gov/application/efhinventory/docs/a10_hms_efh.pdf

    NOAA Fisheries. (2024). Atlantic highly migratory species essential fish habitat 5-year review. https://www.fisheries.noaa.gov/s3/2024-04/Final-HMS-EFH-5-Year-Review-508.pdf

    Norcross, B. L., & Austin, H. M. (1988). Middle Atlantic bight meridional wind component effect on bottom water temperatures and spawning distribution of Atlantic croaker. Continental Shelf Research, 8(1), 69-88. https://doi.org/10.1016/0278-4343(88)90025-8

    North Carolina Division of Marine Fisheries. (2017). Coastal recreational angler’s guide. North Carolina Department of Environmental Quality. https://digital.ncdcr.gov/documents/detail/3689389

    North Carolina Division of Marine Fisheries. (2022). Fishery management plan for interjurisdictional fisheries: Information update. North Carolina Department of Environmental Quality. https://www.deq.nc.gov/marine-fisheries/fisheries-management/interjurisdictional/interjurisdictional-fmp-2022-information-update/open

    North Carolina Division of Marine Fisheries. (2023). North Carolina shrimp fishery management plan: Amendment 1. North Carolina Department of Environment and Natural Resources. https://www.deq.nc.gov/marine-fisheries/fisheries-management/annual-fmp-review/2022/shrimp/open

    North Carolina Division of Marine Fisheries. (2026). Fishery management plan update: Spanish mackerel. North Carolina Department of Environmental Quality. https://www.deq.nc.gov/marine-fisheries/fisheries-management/spanish-mackerel/open

    North Carolina Division of Marine Fisheries. (2026). Fishery management plan update: Black drum. North Carolina Department of Environmental Quality. https://www.deq.nc.gov/marine-fisheries/fisheries-management/black-drum-fmp-update-2026/open

    North Carolina Division of Marine Fisheries. (2026). Fishery management plan update: False albacore. North Carolina Department of Environmental Quality. https://www.deq.nc.gov/marine-fisheries/fisheries-management/false-albacore-fmp-update-2026-0/open

    North Carolina Wildlife Resources Commission. (2025). 2025 North Carolina Wildlife Action Plan. https://www.ncwildlife.gov/state-wildlife-action-plan

    Omori, K. L., & Fisher, R. A. (2017). Summer and fall movement of cownose ray, Rhinoptera bonasus, along the East Coast of United States observed with pop-up satellite tags. Environmental Biology of Fishes, 100(11), 1435-1449. https://doi.org/10.1007/s10641-017-0654-6

    Oswald, J. A., Harvey, M. G., Remsen, R. C., Foxworth, D. U., Cardiff, S. W., Dittmann, D. L., Megna, L. C., Carling, M. D., & Brumfield, R. T. (2016). Willet be one species or two? A genomic view of the evolutionary history of Tringa semipalmata. The Auk, 133(4), 593-614. https://doi.org/10.1642/auk-15-232.1

    Packer, D. B. (1999). Essential fish habitat source document. Summer flounder, Paralichthys dentatus, life history and habitat characteristics (NOAA Technical Memorandum NMFS-NE-151). National Marine Fisheries Service. https://repository.library.noaa.gov/view/noaa/3149

    Robinson, O. J., McGowan, C. P., & Devers, P. K. (2016). Updating movement estimates for American Black ducks (Anas rubripes). PeerJ, 4, e1787. https://doi.org/10.7717/peerj.1787

    Roskar, G., Morley, J. W., & Buckel, J. A. (2024). Seasonality and relative abundance within an elasmobranch assemblage near a major biogeographic divide. PLOS ONE, 19(6), e0300697. https://doi.org/10.1371/journal.pone.0300697

    Ross, J. L., Stevens, T. M., & Vaughan, D. S. (1995). Age, growth, mortality, and reproductive biology of red drums in North Carolina waters. Transactions of the American Fisheries Society, 124(1), 37-54. https://doi.org/10.1577/1548-8659(1995)124<0037:agmarb>2.3.co;2

    Ross, S. W. (1988). Age, growth, and mortality of Atlantic croaker in North Carolina, with comments on population dynamics. Transactions of the American Fisheries Society, 117(5), 461-473. https://doi.org/10.1577/1548-8659(1988)117<0461:agamoa>2.3.co;2

    Smith, M. A., Mahoney, J., Knight, E. J., Taylor, L., Seavy, N. E., Bailey, O. H., Carbone, M., DeLuca, W., Gonzalez, N. S., Jimenez, M. F., W. O’Bryan, G. M., Rao, N., Witko, C. J., Wilsey, C., & Deppe, J. L. (2022). Bird Migration Explorer. National Audubon Society. https://explorer.audubon.org/

    Stenhouse, I. J., Berlin, A. M., Gilbert, A. T., Goodale, M. W., Gray, C. E., Montevecchi, W. A., Savoy, L., & Spiegel, C. S. (2020). Assessing the exposure of three diving bird species to offshore wind areas on the U.S. Atlantic outer continental shelf using satellite telemetry. Diversity and Distributions, 26(12), 1703-1714. https://doi.org/10.1111/ddi.13168

    Stewart, C. B., & Scharf, F. S. (2008). Estuarine recruitment, growth, and first‐year survival of juvenile red drum in North Carolina. Transactions of the American Fisheries Society, 137(4), 1089-1103. https://doi.org/10.1577/t07-176.1

    Sutherland, D. F., & Fable, Jr., W. A. (1980). Results of a king mackerel (Scomberomorus cavalla) and Atlantic Spanish mackerel (Scomberomorus maculatus) migration study, 1975–79 (NOAA Technical Memorandum NMFS-SEFC-12). National Marine Fisheries Service. https://repository.library.noaa.gov/view/noaa/5385

    Tarr, N. M. (2008). Fall migration and vehicle disturbance of shorebirds at South Core Banks, North Carolina [Master’s thesis]. https://repository.lib.ncsu.edu/items/c75ee0d7-84e5-419b-b90c-e253cf809561

    Tilley, A., López-Angarita, J., & Turner, J. (2013). Effects of scale and habitat distribution on the movement of the southern stingray Dasyatis americana on a Caribbean atoll. Marine Ecology Progress Series, 482, 169-179. https://doi.org/10.3354/meps10285

    Titman, R. D. (n.d.). Red-breasted Merganser (Mergus serrator). In The Birds of North America (443rd ed.). A. Poole & F. Gill.

    Warlen, S. M., & Burke, J. S. (1990). Immigration of larvae of fall/Winter spawning marine fishes into a North Carolina Estuary. Estuaries, 13(4), 453. https://doi.org/10.2307/1351789

    Warlen, S. M., & Chester, A. J. (1985). Warlen, S. M., & Chester, A. J. (1985). Age, growth, and distribution of larval spot, Leiostomus xanthurus, off North Carolina. Fishery Bulletin, 83(4), 587–599. Fishery Bulletin, 83(4), 587-599. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/fish-bull/warlen.pdf

    Watts, B. D., Paxton, B. J., Hines, C., & Anderson, S. K. (2023). Estimating potential menhaden consumption by double-crested cormorants along the coast of North Carolina. Frontiers in Marine Science, 10, 1193429. https://doi.org/10.3389/fmars.2023.1193429

    White, M. L., & Chittenden, Jr., M. E. (1977). Age determination, reproduction, and population dynamics of the Atlantic croaker, Micropogonias undulatus. Fishery Bulletin, 75(1), 109-123.

  • Mapping the Invisible Structure: Fish on the Move in the Surf Zone

    Mapping the Invisible Structure: Fish on the Move in the Surf Zone

    Somewhere between watching my daughter catch waves and standing in the surf zone waiting for the next decent one to come through, I noticed the fish.

    They were small—anchovy-like from where I stood, although the glare on the water and the constant movement made identification nearly impossible. What caught my attention wasn’t what they were. It was the fish on the move beside us, all traveling in the same narrow line for almost four hours.

    They were moving parallel to the beach in a line perhaps four inches wide, almost exactly where the waves were breaking.

    A wave would come through hard enough to knock us backward. Water rushed toward shore and then pulled against our legs as it returned. My daughter and I moved with it.

    The fish didn’t seem to.

    The line continued.

    A little farther offshore was another line of larger fish. They were less tightly packed, but moving along the same general stretch of coast. Beyond them, one or two long, slender fish held near my daughter’s board. We couldn’t identify them with certainty, although their shape was consistent with one of our larger needlefishes, possibly a houndfish. They didn’t appear to be simply passing through. They would dart toward the smaller fish, take one, and return.

    Farther still, just beyond the breakers, something much larger came partly out of the water while apparently feeding. It happened too quickly to tell whether it was a shark, large fish, or something else.

    Then the line of little fishes passing in front of me suddenly broke.

    Fish scattered and began leaping from the water, fleeing something I couldn’t see. Almost immediately, there seemed to be another pursuit underway.

    That seemed like a good time for us to take a short break on the beach.

    We had been in the water for nearly four hours by then, and those little fish had been passing us for much of it.

    It was only after watching them for so long that the strange part became obvious.

    The water looked like one place. We had been watching fish on the move through the surf zone all afternoon. 

    The fish were behaving as though it wasn’t.

    The Line That Didn’t End

    Standing in the surf, it is easy to think of the shallow water as a temporary place.

    Waves arrive. Water runs up the beach and retreats. Sand shifts beneath your feet. A few yards offshore, another wave rises over a bar and breaks. Everything seems to be moving too much for anything resembling a pathway to exist.

    To a fish, however, that same water contains structure.

    Even water only a few inches or a foot deep can hold its own patterns. Small runnels form behind sandbars, wave energy changes as water crosses them, and fishes can move parallel to shore through these shallow strips rather than spreading evenly across the surf. The exact species may change from beach to beach, but the pattern is not unusual: fishes sort themselves through very small differences in shallow-water habitat (Layman, 2000).

    Look closely and the tiny fish begin to appear—a narrow line moving through water that, at first glance, looks almost empty. | Image credit: A. Mitchell
    Look closely and the tiny fish begin to appear—a narrow line moving through water that, at first glance, looks almost empty. | Image credit: A. Mitchell

    Late summer can make those patterns especially noticeable. Along our part of the coast, both the number of fish and the variety of species using the surf climb through the warm months, reaching their highest levels from June through August (North Carolina Sea Grant, 2019).

    So the little fish moving past our legs weren’t occupying empty water between the beach and the ocean.

    They were inside habitat. And habitat has shape.

    Mapping the Invisible Structure

    Most of that shape disappears when we look across the water from shore.

    We can see the obvious pieces. Waves often reveal where a sandbar rises toward the surface. Darker water may hint at a trough. A break in the waves can sometimes betray a deeper channel. Farther out, the water deepens into another shade.

    For a small fish, those changes don’t have to be dramatic to matter.

    A few inches of depth can change how quickly the water moves, how much wave energy reaches a spot, what food passes through and which animals can follow. Temperature and wave conditions add another layer. Together, they turn what looks like one open stretch of surf into a collection of much smaller usable spaces (Olds et al., 2018).

    The difference between standing here and standing three feet farther out may barely register to us.

    To a fish only a few inches long, it can mean different water.

    That becomes easier to picture when we pull back and look at the coast beneath us.

    Off Onslow County, the continental shelf doesn’t plunge quickly into deep water. It stretches gradually away from shore across a broad, shallow part of Onslow Bay. Near the beach, the bottom is mostly sand, with shell fragments and coarser material mixed through some areas. Closer to shore, that otherwise gentle slope is interrupted again and again by the smaller features we actually feel beneath our feet—bars, dips, troughs and runnels that waves and currents continually reshape (North Carolina Coastal Resources Commission Science Panel, 2026; Tyler & Kowalewski, 2018).

    Along the Onslow County coast, the shallow sandy bottom rises and falls in subtle bars, troughs, and runnels that can shape how fish use the surf zone. | Image credit: A. Mitchell
    Along the Onslow County coast, the shallow sandy bottom rises and falls in subtle bars, troughs, and runnels that can shape how fish use the surf zone. | Image credit: A. Mitchell

    To us, one of those dips may simply feel like the water suddenly came a little higher on our bodies.

    For a fish only a few inches tall, it can be a different piece of the landscape.

    That doesn’t mean the little school we watched was tracing a particular underwater trough. We couldn’t see the bottom well enough to know that.

    But their persistence was revealing something.

    Waves repeatedly pushed us out of position while fish continued moving through approximately the same narrow part of the surf. Whatever they were responding to—depth, current, food, protection, or some combination—the fish could perceive differences in that water that we couldn’t.

    Their movement made some of the invisible structure visible.

    Why the Smallest Fish Remain Close to Shore

    There is something counterintuitive about watching tiny fish choose the place where waves are breaking. It doesn’t look protected.

    For us, it was the part of the water most likely to knock us over.

    But safety underwater doesn’t necessarily look like calm water.

    For a small fish, extremely shallow water can make life more difficult for some of the animals trying to catch it. A larger predator may still enter—and plenty do—but depth, turbulence and room to maneuver change as the water shoals toward the beach. Juvenile fishes can shift into different depths as they balance the food available there against the risk of being eaten, so sometimes moving only a little shallower can change the odds (Layman, 2000; Miltner et al., 1995; Munsch et al., 2016).

    The breaking surf may look rough and exposed to us, but for small fish, shallow water can change both access to food and the odds of being caught by a larger predator. | Image credit: A. Mitchell
    The breaking surf may look rough and exposed to us, but for small fish, shallow water can change both access to food and the odds of being caught by a larger predator. | Image credit: A. Mitchell

    And there is plenty to eat.

    During summer, some of the smallest schooling fishes—including bay anchovies, striped anchovies and Atlantic silversides—feed largely on plankton carried through the surf. Summer zooplankton can include copepods, mysids, crab larvae and other tiny animals whose numbers shift with tides and time of day (DeLancey, 1987, 1989). Other fishes take food from the sand itself, including mole crabs, passing energy from animals buried beneath the beach into fishes farther up the food web. Surveys of southeastern surf zones have found dozens of species of fish and swimming invertebrates moving through these waters over the seasons (Anderson et al., 1977).

    Even some of the food at the very bottom of that web is being produced right there. The phytoplankton growing in southeastern North Carolina’s surf can make these shallow waters considerably more productive than the coastal ocean just offshore, although not as productive as our estuaries (Cahoon et al., 2017).

    There is something else happening in all that breaking white water too.

    Warm water cannot hold as much oxygen as cooler water. But every time a wave breaks, it churns air into the water. On a hot August day, the same foam and bubbles tossing us around are also helping oxygen move between the air and the shallows (Deike, 2022).

    That doesn’t mean the fish were following an oxygen-rich pathway. We couldn’t know that from what we saw. It is simply another reminder that the breaking surf is not just rougher water. Physically and chemically, things are happening there that are different from the calmer water only a short distance away.

    The water washing around our ankles is therefore not simply the edge of somewhere more biologically important. It produces food, carries food, exchanges gases with the air—and fishes use it.

    That makes the shallow surf something more complicated than a hiding place. A young fish may be balancing several things at once: finding enough food, spending as little energy as possible to get it, and remaining somewhere its chances of becoming food are lower. Different species solve that problem differently.

    Juvenile Florida pompano and gulf kingfish offer a good example. Rather than constantly traveling along the coastline, some can remain surprisingly attached to particular stretches of surf-zone nursery habitat for weeks (Ross & Lancaster, 2002).

    So even a fish that appears to be traveling may still be working within a familiar piece of shoreline—feeding through it, shifting with the tide, or repeatedly using the same shallow habitat.

    The scale of movement matters as much as the movement itself.

    The Edge Is Where Dinner Waits

    Where prey gather predictably, predators gain an advantage too.

    That made the behavior we saw especially interesting. Houndfish, one possible match for those long fish, are large needlefishes built to take other fish, and the ones near us seemed less interested in charging through the entire school than in picking off individuals. They waited, darted toward the passing fish, took one, then returned to approximately the same area. Meanwhile, the line of small fishes carried on like nothing had occurred.

    Farther out, where the water had changed to deep green, something much larger appeared to be doing its own version of the same thing. Whatever the animal was, we saw it break the surface more than once in approximately the same area while fish were there.

    A predator doesn’t have to search every yard of open water equally.

    Sometimes the predator is little more than a glimpse. A small fin breaking the surface (upper right of image) can be the only visible clue that something larger is working the same patch of water as the baitfish. | Image credit: A. Mitchell
    Sometimes the predator is little more than a glimpse. A small fin breaking the surface (upper right of image) can be the only visible clue that something larger is working the same patch of water as the baitfish. | Image credit: A. Mitchell

    Schooling fishes gather where conditions favor them, and those concentrations can be shaped by depth, temperature, currents and other physical features. When prey collect in one place instead of being scattered widely, feeding opportunities become concentrated there too (Goetsch et al., 2023; Olds et al., 2018).

    Surf fishermen have been reading that relationship from above the water for generations. A trough, a cut through a sandbar or a sudden concentration of bait can be a clue not only to where the smaller fish are gathering, but to where something larger may come looking for them (Ward, n.d.).

    What looked from our perspective like separate layers of fish may therefore have been something more dynamic.

    The smallest fish were using conditions that suited them. Their concentration, in turn, created an opportunity for a predator capable of working alongside that concentration. What gave one animal access to plankton or a little more protection could simultaneously make it easier for another animal to find dinner.

    The fish may disappear beneath the surface, but the water can still give it away—a brief wake or disturbance marking movement that is otherwise hidden from view. | Image credit: A. Mitchell
    The fish may disappear beneath the surface, but the water can still give it away—a brief wake or disturbance marking movement that is otherwise hidden from view. | Image credit: A. Mitchell

    It wasn’t simply a food chain conveniently lined up from smallest fish near shore to largest predator offshore. Each animal was using the same physical landscape differently, and one animal’s useful habitat could become another animal’s hunting ground.

    The structure beneath the water wasn’t just organizing where fish could move.

    It was helping organize where encounters between them could happen.

    When the Line Breaks

    The fish themselves add another layer.

    Once individuals gather into a school, they begin responding not only to the water and predators around them, but to one another.

    “Safety in numbers” captures only part of what that accomplishes. A fish in a school has neighbors watching in many directions, and information about danger can move rapidly through the group. Individuals continually adjust their spacing and direction in response to nearby fish, habitat and perceived threats, so a school can tighten, turn or reorganize without every fish having to detect the predator independently (Munsch et al., 2016).

    There are tradeoffs. A large school may be easier to notice than a lone fish, and crowding means sharing food and space. But once a predator attacks, the group can make choosing and isolating a single target much harder. Instead of one fish moving through open water, the predator encounters many similar bodies changing direction almost at once.

    And all of that coordination has to happen while the water beneath them is moving too.

    A school in the shallow surf isn’t reacting to a predator against a blank background. Depth is changing. Waves are passing through. Currents are pushing alongshore and back toward the sea. The fish have to stay together while continuously adjusting to the landscape around them.

    Then an attack can rearrange everything in seconds.

    A school may compress, turn sharply, split apart, or scatter as the threat moves through it. Sometimes the quickest route away is upward, and baitfish begin breaking the surface.

    Sometimes the chase shows itself before the predator does. A small patch of agitated water can be the only sign that the school beneath the surface has suddenly changed direction. | Image credit: A. Mitchell
    Sometimes the chase shows itself before the predator does. A small patch of agitated water can be the only sign that the school beneath the surface has suddenly changed direction. | Image credit: A. Mitchell

    From above, that sudden spray of little bodies can look almost disconnected from what caused it. The predator may never become visible at all. What we see is the response moving through the school—the orderly shape breaking apart and reforming as hundreds of tiny decisions happen at once.

    The line, in other words, was never simply a line.

    It was a coordinated group whose shape could change almost instantly when the balance between traveling, feeding and surviving changed.

    Just Beyond the Breakers

    The surf zone doesn’t end at a precise biological boundary where the last wave breaks.

    The water on either side of that breaker is connected, but the conditions are changing. Depth increases. The bottom falls farther away. Wave energy changes. Animals that can move comfortably through one part of that gradient may use another part differently, and fishes can cross between them as their needs change (Olds et al., 2018).

    Beyond the shallow surf, the water deepens and the habitat changes with it—but the boundary is not a hard line. Fish move back and forth across that transition as their needs change. | Image credit: A. Mitchell
    Beyond the shallow surf, the water deepens and the habitat changes with it—but the boundary is not a hard line. Fish move back and forth across that transition as their needs change. | Image credit: A. Mitchell

    That makes the surf less like a row of separate habitats and more like a transition.

    On the landward side are the shallow runnels and troughs used by small fishes. Farther out, those waters connect with the open nearshore ocean. Along the beach, the same surf runs toward inlets, and beyond those inlets lie estuaries and nursery habitats. For a fish, these aren’t necessarily separate places encountered one at a time. They can be connected parts of its life.

    That connection becomes particularly important for young fishes.

    Some species arrive in shallow coastal waters during early life stages. Others move between estuarine nurseries and the ocean as they grow. Still others use the surf primarily to feed or travel. The importance of any one patch of shallow water therefore depends partly on what it connects to (Olds et al., 2018; Ross & Lancaster, 2002).

    Predators cross those connections as well. As prey move into deeper water, toward an inlet or along the shoreline, they become available to a different mix of animals. Conversely, a predator following prey does not need to remain on one side of a line humans call “the breakers.”

    The larger animal we glimpsed offshore isn’t evidence of a particular cross-shore food chain. We don’t know what it was, what it caught, or why it was feeding there.

    What its presence does illustrate is that the ecological landscape continues beyond what we can easily see from knee- or waist-deep water.

    The surf is an edge, but it is also a bridge.

    Movement Within Movement

    Follow that bridge along the North Carolina coast and the scale changes again.

    Our long stretches of open beach are repeatedly interrupted by inlets, and behind those inlets lie sounds, tidal creeks, marshes and estuaries. To us, those places often have separate names and boundaries. To a fish moving through them, they are connected pieces of habitat used at different times and for different reasons.

    The surf itself can be both a place to feed and a route between those places (Olds et al., 2018). A juvenile using shallow water may later move deeper, follow the coast toward an inlet, or leave a nursery area as it grows. Another fish may do almost the opposite and remain surprisingly local. Juvenile Florida pompano and gulf kingfish tagged along southeastern North Carolina beaches, for example, could remain faithful to relatively small areas of surf for extended periods (Ross & Lancaster, 2002).

    A few feet with the tide, weeks along one beach, a journey between estuary and ocean, or a seasonal movement along hundreds of miles of coastline can therefore all belong to the same animal at different times in its life.

    What looks like one continuous stretch of water can connect very different habitats—from the shallow surf to inlets, estuaries, and the nearshore ocean. | Image credit: A. Mitchell
    What looks like one continuous stretch of water can connect very different habitats—from the shallow surf to inlets, estuaries, and the nearshore ocean. | Image credit: A. Mitchell

    Those aren’t separate stories.

    They fit inside one another.

    That is what makes a shallow stretch of surf important even when it is not a final destination. It may be feeding ground, nursery habitat, temporary refuge, travel corridor—or simply the connective piece that allows a fish to reach the next habitat it needs.

    The coastline is not only habitat made of places.

    It is habitat made of connections between them.

    The Late-Summer Coast

    By August, many of those connections are busy.

    The surf fills with its greatest abundance and variety of fishes during the warm months from June through August (North Carolina Sea Grant, 2019). The shallowest surf holds its greatest abundance and diversity during this part of the year (Layman, 2000).

    For someone walking into warm August water, that means the crowd beneath the surface can be very different from the one occupying the same beach in winter.

    By late summer, the shallow surf can look almost unchanged from day to day while the mix of fish moving through it shifts with temperature, tide, food, and life stage. | Image credit: A. Mitchell
    By late summer, the shallow surf can look almost unchanged from day to day while the mix of fish moving through it shifts with temperature, tide, food, and life stage. | Image credit: A. Mitchell

    Some of the year’s young fishes have had months to grow. Seasonal changes in plankton and animals living on and beneath the sand alter the food available to them, while water temperature, tides, waves and each species’ own life cycle influence which fishes are present and where they spend their time (Anderson et al., 1977; DeLancey, 1987, 1989; Olds et al., 2018; Wickliffe et al., 2019).

    Those changes ripple upward. Small fishes link plankton and other tiny prey with larger predatory fishes, and dense gatherings of forage fish can create concentrated feeding opportunities for predators higher in the food web (Goetsch et al., 2023).

    But even “late summer” doesn’t describe one fixed community.

    The tide can rearrange the shallow habitat over the course of hours. More species enter the very shallow surf at high tide than at low tide, and the community changes again after dark as adult predators move into water they use differently during the day (Layman, 2000).

    Temperature, tide, light and life stage change it.

    All of those cycles overlap along a coastline where animals are also arriving, leaving, feeding, growing and moving between habitats.

    The shoreline may stay in the same place on our map.

    Ecologically, it is never quite the same place twice.

    Looking at the Water Differently

    What began as an odd little line of fish turned out to be a glimpse of several things happening at once.

    The shallow surf had physical structure even where we couldn’t clearly see it. That structure could change where food collected, where small fishes found useful habitat, and where predators encountered prey. The schools themselves added another layer, responding not only to the water around them but to one another. Beyond them, the surf connected outward toward deeper water and alongshore toward inlets, estuaries and larger movements taking place along the coast.

    None of that requires every fish we saw to have been following a migration route.

    In some ways, that makes the afternoon more interesting.

    Movement in the ocean doesn’t begin with the thousand-mile journey of a shark or a sea turtle. It can begin with an animal responding to a few inches of depth, a shifting tide, a patch of food or the sudden arrival of a predator. Those small decisions accumulate across schools, habitats, seasons and coastlines until they become some of the larger patterns we recognize.

    None of those animals needed the boundaries to be visible to us.

    The fish were already responding to depth, water movement, food, risk, season and one another. Their paths crossed a landscape hidden beneath waves and glare.

    Maybe that is one of the easiest things to miss when we stand at the edge of the ocean.

    We look out and see water.

    Sometimes, if we stay there long enough, the animals begin drawing the map.

    Once you know what to look for, the water stops looking empty. Larger fish move through the same surf that, from a distance, can seem almost featureless. | Image credit: A. Mitchell
    Once you know what to look for, the water stops looking empty. Larger fish move through the same surf that, from a distance, can seem almost featureless. | Image credit: A. Mitchell

    References

    Allen, L. G., & Pondella II, D. J. (2006). Surf zone, coastal pelagic zone and harbors. In The Ecology of Marine Fishes: California and Adjacent Waters (pp. 149-166). University of California Press.

    Anderson, W. D., Dias, J. K., Dias, R. K., Cupka, D. M., & Chamberlain, N. A. (1977). The Macrofauna of the surf zone off folly beach, South Carolina (NMFS SSRF-704). NOAA. https://books.google.com/books?hl=en&lr=&id=EKM2rRmrBEYC&oi=fnd&pg=PA1&dq=+fish+behavior+in+the+surf+zone+north+carolina&ots=ZzlY5Ddul_&sig=bBAuFw1u6Pi4TS-fb2fJhId2cSk#v=onepage&q&f=false

    Cahoon, L. B., Bugica, K., Wooster, M. K., & Dickens, A. K. (2017). Factors affecting surf zone phytoplankton production in southeastern North Carolina, USA. Estuarine, Coastal and Shelf Science, 196, 269-275. https://doi.org/10.1016/j.ecss.2017.07.012

    Deike, L. (2022). Mass transfer at the ocean–atmosphere interface: The role of wave breaking, droplets, and bubbles. Annual Review of Fluid Mechanics, 54(1), 191-224. https://doi.org/10.1146/annurev-fluid-030121-014132

    DeLancey, L. B. (1987). The summer zooplankton of the surf zone at Folly Beach, South Carolina. Journal of Coastal Research, 3(2). https://journals.flvc.org/jcr/article/view/77561

    DeLancey, L. B. (1989). Trophic relationship in the surf zone during the summer at Folly Beach, South Carolina. Journal of Coastal Research, 5(3). https://journals.flvc.org/jcr/article/view/78162

    Goetsch, C., Gulka, J., Friedland, K., Winship, A., Clerc, J., Gilbert, A., Goyert, H., Stenhouse, I., Williams, K., Willmott, J., Rekdahl, M., Rosenbaum, H., & Adams, E. (2023). Surface and subsurface oceanographic features drive forage fish distributions and aggregations: Implications for prey availability to top predators in the US Northeast shelf ecosystem. Ecology and Evolution, 13(7), e10226. https://doi.org/10.22541/au.167163077.72855489/v1

    Harris, S. (2024, September 19). Finding fish in lots of water. Coastwatch. https://ncseagrant.ncsu.edu/coastwatch/finding-fish-in-lots-of-water

    Koval, G. N., Dugan, J. E., & Hamilton, S. L. (2025). Seasonal variation and response of surf zone fish assemblages to environmental variables in the Northeast Pacific. Continental Shelf Research, 293, 105526. https://doi.org/10.1016/j.csr.2025.105526

    Layman, C. (2000). Fish assemblage structure of the shallow ocean surf-zone on the Eastern Shore of Virginia barrier islands. Estuarine, Coastal and Shelf Science, 51(2), 201-213. https://doi.org/10.1006/ecss.2000.0636

    Miltner, R. J., Ross, S. W., & Posey, M. H. (1995). Influence of food and predation on the depth distribution of juvenile spot (Leiostomus xanthurus) in tidal nurseries. Canadian Journal of Fisheries and Aquatic Sciences, 52(5), 971-982. https://doi.org/10.1139/f95-096

    Munsch, S., Cordell, J., & Toft, J. (2016). Fine-scale habitat use and behavior of a nearshore fish community: Nursery functions, predation avoidance, and spatiotemporal habitat partitioning. Marine Ecology Progress Series, 557, 1-15. https://doi.org/10.3354/meps11862

    N.C. Coastal Resources Commission Science Panel. (2026). Effects of Hard Structures on Sandy, Open-Ocean Coastlines. N.C. Department of Environmental Quality, Division of Coastal Management. https://www.deq.nc.gov/coastal-management/draft-science-panel-report-effects-hard-structures-june-15-2026-v3

    North Carolina Sea Grant. (2023, July 27). What fish species live in the surf zone? Hook, Line and Science. https://ncseagrant.ncsu.edu/hooklinescience/what-fish-species-live-in-the-surf-zone

    Olds, A. D., Vargas‐Fonseca, E., Connolly, R. M., Gilby, B. L., Huijbers, C. M., Hyndes, G. A., Layman, C. A., Whitfield, A. K., & Schlacher, T. A. (2017). The ecology of fish in the surf zones of ocean beaches: A global review. Fish and Fisheries, 19(1), 78-89. https://doi.org/10.1111/faf.12237

    Parker, R., & Ross, S. W. (1986). Observing reef fishes from submersibles off North Carolina. Northeast Gulf Science, 8(1). https://doi.org/10.18785/negs.0801.03

    Ross, S. W., & Lancaster, J. E. (2002). Movements and site fidelity of two juvenile fish species using surf zone nursery habitats along the southeastern North Carolina coast. Environmental Biology of Fishes, 63(2), 161-172. https://doi.org/10.1023/a:1014287917297

    Tyler, C. L., & Kowalewski, M. (2018). Regional surveys of macrobenthic shelf invertebrate communities in Onslow Bay, North Carolina, U.S.A. Scientific Data, 5(1). https://doi.org/10.1038/sdata.2018.54

    Ulanski, S. (2011). Fishing North Carolina’s Outer Banks: The complete guide to catching more fish from surf, pier, sound, and ocean. University of North Carolina Press.

    Wickliffe, L. C., Rhode, F. C., Riley, K. L., & Morris, Jr., J. A. (2019). An assessment of fisheries species to inform time-of-year restrictions for North Carolina and South Carolina (NOS NCCOS 263). NOAA Technical Memorandum. https://coastalscience.noaa.gov/data_reports/an-assessment-of-fisheries-species-to-inform-time-of-year-restrictions-for-north-carolina-and-south-carolina/

    Wilber, D., Clarke, D., Ray, G., & Burlas, M. (2003). Response of surf zone fish to beach nourishment operations on the northern coast of New Jersey, USA. Marine Ecology Progress Series, 250, 231-246. https://doi.org/10.3354/meps250231

  • Where the Water Moves Before the Storm: Sharks, Estuaries, and the Illusion of Shelter in Onslow County

    Where the Water Moves Before the Storm: Sharks, Estuaries, and the Illusion of Shelter in Onslow County

    Where the Water Turns Before the Storm

    There’s a version of this story that shows up often—sometimes in films, sometimes in passing explanations—that when a large storm approaches, sharks move into estuaries to escape the violence of the open ocean.

    It makes intuitive sense.

    The ocean becomes something unmanageable—waves building, wind stacking energy across the surface. And just inland, the estuary appears contained. Narrower. Protected. A place where the water feels like it should be quieter.

    But if you stand at the edge of a tidal creek before a storm, what you see first isn’t protection.

    It’s change.

    The surface tightens. Wind presses across it—not yet breaking it into waves, but organizing it into long, directional movement. The irregular texture of a normal day disappears into something aligned. Purposeful.

    Water levels begin to rise before rainfall arrives. The boundary between water and marsh softens. Spartina no longer holds a sharp edge. The ground beneath your feet gives way more easily, saturated beyond its usual resistance.

    Water moving through a beach access during storm conditions, as rising levels and wind-driven flow begin to overtake the boundary between ocean and land. | Image credit: Jaime Armstrong
    Water moving through a beach access during storm conditions along the North Carolina coast, as rising levels and wind-driven flow begin to overtake the boundary between ocean and land. | Image credit: J. Armstrong

    This is the first shift.

    Not force, but redistribution.

    And everything in the system is already responding.

    What Lives Here When the System Starts Moving

    The sharks that use estuaries are not here because these places offer protection from storms.

    They are here because of what you can’t always see at first glance.

    A juvenile blacktip shark (Carcharhinus limbatus) doesn’t move through open water the way people imagine sharks do. It stays in the shallows—along the edges where the water darkens slightly, where small schools of fish break apart and reform, where the bottom shifts from sand to scattered shell. These areas are harder for larger predators to move through quickly. Not impossible—but slower, more complicated.

    Blacktip sharks move through estuaries in Onslow County, North Carolina, using shallow coastal water where movement, depth, and structure shape where they travel. | Image credit: kseym001. iNaturalist
    Blacktip sharks move through estuaries in Onslow County, North Carolina, using shallow water where depth, structure and movement shape where they travel. | Image credit: kseym001, iNaturalist

    That difference matters when you’re small.

    What scientists describe as “structure” is this: broken bottom, uneven depth, patches of grass, oyster shell, shadow, current seams. From the shoreline, it just looks like variation. To a young shark, it’s the difference between being exposed and being able to disappear for a second.

    That’s why these areas are used as nurseries—not because they are safe, but because they are less predictable in a way that favors smaller animals (Heupel et al., 2007).

    From a distance, it looks like open water. Up close, it’s a series of edges—grass, mud, and channels—where movement slows, shifts, and concentrates. | Image credit: A. Mitchell
    From a distance, it looks like open water. Up close, it’s a series of edges—grass, mud, and channels—where movement slows, shifts, and concentrates. | Image credit: A. Mitchell

    An Atlantic sharpnose shark (Rhizoprionodon terraenovae) uses that same space differently. You wouldn’t see it cruising the center of a channel. You’d find it where things intersect—along the drop where shallow water slips into deeper flow, near the edges of grass beds, or where current carries small prey out of the marsh and into open water.

    It’s not avoiding predators in the same way a juvenile blacktip is.

    It’s positioning itself where food moves, while still staying just out of the most exposed water (Ulrich et al., 2007).

    Even the bonnethead shark (Sphyrna tiburo)—often described as a “benthic feeder”—is easier to understand if you ignore the word and watch the behavior. It spends time over the bottom, moving slowly across seagrass beds and sandy patches, nosing through the substrate for crabs and small invertebrates.

    You’re most likely to notice it not by seeing the whole animal, but by the movement it leaves behind.

    A subtle disturbance. A shift in the grass. A shape that doesn’t hold still long enough to resolve.

    It’s also one of the few sharks you’re likely to find deeper into the estuary, where the water begins to lose its salt edge. Bonnetheads can tolerate lower salinity than many coastal sharks, which allows them to follow food farther into these mixed waters rather than staying closer to the inlet (Bethea et al., 2007).

    Not because it’s calmer there.

    Because the feeding opportunities extend into that space.

    These sharks are here because the estuary offers layers—places to feed, places to pass through, places where movement is broken up just enough to matter (Knip et al., 2010; Bangley et al., 2018).

    But all of those layers depend on something staying consistent—edges holding their shape, water moving in predictable directions, and clarity allowing animals to track one another.

    And those are the first things a storm begins to take apart.

    The Problem With “Shelter”

    When a hurricane approaches, an estuary does not become a refuge.

    It becomes harder to read.

    If you stand on the ocean side of Topsail Island, you’ll see the change first as energy—waves building, spacing tightening, the surface lifting and falling with more force than it did the day before. But if you cross to the other side of the island—along the Intracoastal Waterway or into Stump Sound—it doesn’t look like that.

    There, it rises.

    Steadily. Quietly. Without the same visible force.

    And that difference is exactly why the idea of “shelter” feels convincing.

    On the ocean side, the storm is easier to recognize. Energy builds into waves, making the movement visible in a way it isn’t on the other side of the island. | Image credit: WITN-TVFrom this side, it doesn’t look like a storm in the same way. The water rises and shifts along the shoreline, even as the system is already building offshore. | Image credit: A. Mitchell
    On the ocean side, the storm is easier to recognize. Energy builds into waves, making the movement visible in a way it isn’t on the other side of the island. | Image credit: WITN-TV. On the sound side, it doesn’t look like a storm in the same way. The water rises and shifts along the shoreline, even as the system is already building offshore. | Image credit: A. Mitchell

    Under normal conditions, these waters are connected—but they don’t move together. Ocean tides enter through New River Inlet and New Topsail Inlet, then work their way through the back-barrier system—the marshes, the Intracoastal, the sounds. That movement slows as it spreads out, which is why tides behind the island can lag the ocean by hours (Friedrichs & Aubrey, 1988).

    From the shoreline, it feels like separation.

    Like the ocean is doing one thing, and the water behind the island is doing another.

    As a storm approaches, that timing begins to compress. Wind pushes water through the inlets faster than the system can distribute it, while water already inside has less opportunity to drain back out.

    What was once staggered in time begins to overlap.

    Storm surge doesn’t just raise water levels—it disrupts the normal exchange between ocean and estuary, forcing water inland and holding it there longer than a typical tidal cycle (National Oceanic and Atmospheric Administration, 2023).

    That’s why the sound side doesn’t look violent at first.

    It’s not because it’s protected.

    It’s because it’s filling.

    You can watch it happen without measuring anything. The usual drop after high tide doesn’t come when you expect it. Water continues to rise or holds in place. The difference between ocean and sound begins to disappear—not because the ocean calms down, but because the back-barrier system begins to behave more like a single body of water under pressure.

    Edges blur as marsh grass floods from below. The bottom disappears as suspended sediment increases, and runoff and resuspension mix material into the water column faster than it can settle (Mallin et al., 1999).

    The system is no longer cycling. It’s shifting faster than it can recover, with the patterns that usually hold it together breaking down in real time (Resh et al., 1988).

    It’s accumulating.

    And once that happens, the things that made this environment usable begin to disappear with it.

    Where the Larger Sharks Actually Go

    If an estuary loses the very structure that makes it usable during a storm, then the question shifts.

    Sharks are not staying in place and enduring that change.

    They are moving with it.

    But not in the way we tend to imagine.

    They don’t need to move into something more protected, because the ocean itself isn’t uniform. What looks chaotic at the surface is layered, and that layering holds even as a storm passes overhead. Wave energy dissipates quickly with depth, which means that the violence you see from the beach does not extend indefinitely downward.

    A few meters below the surface, movement changes.

    Deeper still, it stabilizes.

    From above, the structure becomes visible—shallow bars, deeper channels, and the connections between ocean and estuary that shape how water moves through the system. | Image credit: Town of Topsail Beach
    From above, the structure becomes visible—shallow bars, deeper channels, and the connections between ocean and estuary that shape how water moves through the system. | Image credit: Town of Topsail Beach

    For larger coastal sharks like the bull shark (Carcharhinus leucas), that difference matters more than distance from shore. They are not choosing between rough ocean and calm estuary.

    They are moving within a three-dimensional space.

    And they sense the change before it arrives. It’s the same shift you feel before a storm—the air getting heavier, the pressure dropping, something changing before you can point to it. In the water, that change travels differently, and sharks begin responding to it well before anything looks different at the surface (Papastamatiou et al., 2015).

    From the shoreline, it can feel like the storm suddenly arrives. But for animals in the water, it doesn’t. The change builds, and they are already moving within it—shifting position, adjusting depth, following the parts of the system that are still holding together as everything else begins to change long before it’s visible from the shoreline (Heupel et al., 2003).

    Where the Shallow-Water Sharks Go

    The sharks that spend their time in these shallow systems don’t have the same options as those offshore, because there is no deeper layer to move into when conditions begin to change. Instead, their response is tied to what parts of the system still hold together. As water levels rise and flow patterns begin to shift, the backs of creeks and the shallowest flats are often the first places to lose definition. These are areas where water can become cut off or overly mixed, where direction is no longer consistent, and where the features that usually structure movement begin to disappear.

    What follows is not a movement further inland, but a gradual pulling back toward places that remain more stable. That often means deeper channels, intersections where water is still moving in a defined direction, or areas closer to inlets where exchange is still occurring. Rather than leaving the estuary entirely, many individuals consolidate within the portions of it that continue to function in a recognizable way. This kind of movement—shifting position as conditions change rather than holding in place—has been observed in coastal sharks as these systems begin to break down (Heupel et al., 2003).

    At the same time, the system itself is expanding beyond its usual boundaries. Storm surge and flooding connect environments that are typically separate, allowing water to move across marsh, into low-lying land, and through built spaces like roads, canals, and retention areas. When that happens, animals already present in the water column move with it, not because they are selecting those environments, but because the physical structure that normally contains them is temporarily absent. Observations of sharks and other marine species in flooded coastal areas are most often associated with these short-lived hydrological connections rather than deliberate movement into unfamiliar habitats (Snelson et al., 1984).

    As water spreads across the landscape, the system expands with it—connecting marsh, channels, and developed areas into a single, continuous space. | Image credit: C. Mitchell, AccuWeather
    As water spreads across the landscape, the system expands with it—connecting marsh, channels, and developed areas into a single, continuous space. | Image credit: C. Mitchell, AccuWeather

    As water recedes, those connections close just as quickly as they formed. The system contracts, and the pathways that briefly allowed movement into those spaces disappear. Animals either move back with the retreating water or are left in conditions that no longer support them. What appears from the outside as unusual behavior is, in most cases, the result of a system that has temporarily lost its boundaries and then reestablished them.

    Where the Assumption Breaks

    The idea that sharks move into estuaries for shelter during storms rests on a simple assumption: that calmer-looking water offers protection. From the shoreline, that assumption is easy to make. The ocean side of Topsail Island shows the storm first—waves building, energy increasing—while the waters behind the island, along the Intracoastal Waterway and within Stump Sound, often appear quieter in the early stages. But that difference is not a separation of systems. It is a difference in timing.

    Under normal conditions, tidal exchange through New River Inlet and New Topsail Inlet distributes ocean energy into the back-barrier environment with a delay, shaped by channel geometry and friction. That lag creates the appearance that one side of the island is responding differently than the other, when in reality both are part of the same connected system (Friedrichs & Aubrey, 1988). As storm conditions intensify, that delay compresses. Water is pushed through the inlets more rapidly than the system can accommodate, and the distinction between ocean and estuary begins to collapse into a single, continuous response driven by surge, wind, and pressure (NOAA, 2023).

    Sharks are responding to that shift the entire time, not by seeking out calm water, but by staying within parts of the system that hold their structure for as long as they can. Offshore, that structure exists vertically, allowing movement into deeper, more stable layers. Within estuaries, it exists horizontally and can disappear quickly as gradients break down. The concept of “shelter” depends on the persistence of those gradients—clear edges, directional flow, and predictable relationships between different parts of the system—but during a storm, those features are among the first to be altered.

    What remains after the storm is not evidence of animals moving into safer spaces, but the memory of contrast between what those spaces usually are and what they became under changing conditions. That contrast is compelling enough to shape interpretation, even when the underlying processes point to a different explanation.

    After the water recedes, the boundary remains shifted—marking where movement passed through, rather than where it began. | Image credit: J. Lester
    After the water recedes, the boundary remains shifted—marking where movement passed through, rather than where it began. | Image credit: J. Lester

    References

    Bangley, C. W., Paramore, L., Shiffman, D. S., & Rulifson, R. A. (2018). Increased abundance and nursery habitat use of the bull shark (Carcharhinus leucas) in response to a changing environment in a warm-temperate Estuary. Scientific Reports, 8(1). https://doi.org/10.1038/s41598-018-24510-z

    Bethea, D., Buckel, J., & Carlson, J. (2004). Foraging ecology of the early life stages of four sympatric shark species. Marine Ecology Progress Series, 268, 245-264. https://doi.org/10.3354/meps268245

    Ebert, D. A., Dando, M., & Fowler, S. (2021). Sharks of the world: A complete guide. Princeton University Press.

    Friedrichs, C. T., & Aubrey, D. G. (1988). Non-linear tidal distortion in shallow well-mixed estuaries: A synthesis. Estuarine, Coastal and Shelf Science, 27(5), 521-545. https://doi.org/10.1016/0272-7714(88)90082-0

    Heupel, M., Carlson, J., & Simpfendorfer, C. (2007). Shark nursery areas: Concepts, definition, characterization and assumptions. Marine Ecology Progress Series, 337, 287-297. https://doi.org/10.3354/meps337287

    Heupel, M. R., Simpfendorfer, C. A., & Hueter, R. E. (2003). Running before the storm: Blacktip sharks respond to falling barometric pressure associated with tropical storm Gabrielle. Journal of Fish Biology, 63(5), 1357-1363. https://doi.org/10.1046/j.1095-8649.2003.00250.x

    Knip, D., Heupel, M., & Simpfendorfer, C. (2010). Sharks in nearshore environments: Models, importance, and consequences. Marine Ecology Progress Series, 402, 1-11. https://doi.org/10.3354/meps08498

    Mallin, M. A., Posey, M. H., Shank, G. C., McIver, M. R., Ensign, S. H., & Alphin, T. D. (1999). Hurricane effects on water quality and benthos in the cape fear watershed: Natural and anthropogenic impacts. Ecological Applications, 9(1), 350. https://doi.org/10.2307/2641190

    NOAA. (2024, June 16). What is storm surge? National Ocean Service website. https://oceanservice.noaa.gov/facts/stormsurge-stormtide.html

    Papastamatiou, Y. P., Watanabe, Y. Y., Bradley, D., Dee, L. E., Weng, K., Lowe, C. G., & Caselle, J. E. (2015). Drivers of daily routines in an ectothermic marine predator: Hunt warm, rest warmer? PLOS ONE, 10(6), e0127807. https://doi.org/10.1371/journal.pone.0127807

    Pine, W. E., Pollock, K. H., Hightower, J. E., Kwak, T. J., & Rice, J. A. (2003). A review of tagging methods for estimating fish population size and components of mortality. Fisheries, 28(10), 10-23. https://doi.org/10.1577/1548-8446(2003)28[10:arotmf]2.0.co;2

    Resh, V. H., Brown, A. V., Covich, A. P., Gurtz, M. E., Li, H. W., Minshall, G. W., Reice, S. R., Sheldon, A. L., Wallace, J. B., & Wissmar, R. C. (1988). The Role of Disturbance in Stream Ecology. Journal of the North American Benthological Society; Freshwater Science, 7(4). https://doi.org/10.2307/1467300

    Ulrich, G. F., Jones, C. M., Driggers III, W. B., Drymon, J. M., Oakley, D., & Riley, C. (2007). Habitat Utilization, Relative Abundance, and Seasonality of Sharks in the Estuarine and Nearshore Waters of South Carolina. American Fisheries Society Symposium, 50, 125-139. https://lowcountryinstitute.org/images/research/dox/Ulrichetal2007.pdf

    Valiela, I., & Cole, M. L. (2002). Comparative evidence that salt marshes and mangroves may protect seagrass meadows from land-derived nitrogen loads. Ecosystems, 5(1), 92-102. https://doi.org/10.1007/s10021-001-0058-4

  • Dolphins of Onslow County Waters: Ecology and Shared Shoreline

    Dolphins of Onslow County Waters: Ecology and Shared Shoreline

    Dolphins of Onslow County: A Coastal Population

    There is often a moment before you see them.

    A breath breaks the air first — a soft exhale that sounds almost human — and then a dorsal fin lifts from the channel like a line drawn through moving water. The tide is falling. Gulls hover over the seam where current tightens. Fishermen pause mid-cast because everyone knows the rhythm: if the dolphins are working the edge, the fish are already gathering.

    These encounters feel spontaneous, but they are not accidents. The dolphins that surface beside our piers, marsh creeks, and inlets are not anonymous travelers passing through. Many bottlenose dolphins show long-term site fidelity and structured community patterns in estuarine systems, returning to the same places across years (Urian et al., 2009; Wells, 2014). To live on this shoreline is to share space with minds moving just below the surface — residents of the tidal edge.

    Who they are: a coastal population

    The dolphins most frequently seen along Onslow County’s waters are common bottlenose dolphins (Tursiops truncatus), a species whose “coastal” lives can look very different from “offshore” lives. Across the western North Atlantic, genetic studies show fine-scale population structure that can separate dolphins using nearshore coastal waters from dolphins using inshore estuarine waters (Rosel et al., 2009). More broadly, integrative work continues to support meaningful coastal vs offshore divergence in the region (Costa et al., 2022).

    In estuaries, photo-identification research (matching dorsal-fin markings) repeatedly shows that bottlenose dolphins can form discrete social communities with limited spatial overlap — a pattern consistent with long-term residency and local familiarity (Urian et al., 2009). In practical terms, the dolphin a child watches from a dock in spring may be seen again the following winter, and again the next year: not a rumor, but a biological possibility supported by long-term studies of resident dolphins elsewhere on the coast (Wells, 2014).

    Photo-identification doesn’t always rely solely on human matching of fin shapes; new tools such as machine learning are being developed to improve accuracy in identifying individual dolphins and whales in the wild. For example, researchers in Hawaii are using advanced algorithms to distinguish individuals from large photo libraries of dorsal fins. As technology improves, methods like photo-ID only get more reliable — which means studies of habitat overlap and seasonal return become more precise over time.

    An inside look at how scientists “read” dorsal fin shapes and markings to track the same dolphins over time.

    Reading the geometry of the estuary

    Dolphins do not simply occupy estuaries; they interpret them.

    Tidal channels function as moving architecture. Falling tides compress fish schools toward narrowing exits. Sandbars redirect flow into faster seams. Marsh edges trap prey against shallow gradients. Dolphins exploit these features with precision, repeatedly targeting conditions that make prey capture more efficient (Barros & Wells, 1998; Torres & Read, 2009).

    This is one reason dolphins so often appear where the water “looks alive” — at convergence lines, inlet throats, and channel bends. In Florida Bay, for example, foraging tactics are mapped onto habitat features that define where dolphins have spent their time, thus turning behavior into geography (Torres & Read, 2009). What seems like play from shore can be highly strategic predation.

    Bottlenose dolphins breaching off Seaview Pier, N. Topsail Beach, North Carolina. The arc of the body and column spray reflect the mechanics of propulsion - force directed through the tail, momentum carried into the air. | Photo credit: Howard Crumpler Photography, 2026
    Bottlenose dolphins breaching off Seaview Pier, N. Topsail Beach, North Carolina. The arc of the body and column spray reflect the mechanics of propulsion – force directed through the tail, momentum carried into the air. | Photo credit: Howard Crumpler Photography, 2026

    Reader Question:

    Why do dolphins seem more active on rainy or overcast days?

    Weather, light, and the illusion of play

    You may notice that dolphins seem especially active on overcast or rainy days — surfacing more frequently, breaching, or moving in tight arcs through wind-rippled water. It can look like preference, even mood. But dolphins are responding less to cloud cover than to what cloud cover does to the water.

    When the sky darkens, baitfish don’t stay arranged the same way. They may bunch together or rise toward the surface. For a predator already working those upper layers, that shift can make hunting more efficient (Benoit-Bird & Au, 2003). Wind and rain can also stir the surface and cloud the water, changing who sees whom first (De Robertis et al., 2003).

    There is also a perceptual component. Overcast skies reduce glare, making dorsal fins and splashes easier for human observers to detect. Wind-textured water highlights movement. What appears to be “more play” may sometimes be improved visibility — a reminder that observer experience and animal behavior are not always the same phenomenon.

    In short, dolphins are responding to ecological conditions. The weather alters the water; the water alters the fish.

    Two bottlenose dolphins break the surface beneath the gray horizon off Surf City, North Carolina. Overcast light and wind-roughened water can change how fish move – and how easily we notice the dolphins following them. | Photo credit: Johnny Provost, Jr., 2025
    Two bottlenose dolphins break the surface beneath the gray horizon off Surf City, North Carolina. Overcast light and wind-roughened water can change how fish move – and how easily we notice the dolphins following them. | Photo credit: Johnny Provost, Jr., 2025

    Communication and social intelligence

    Bottlenose dolphins have been studied for decades not just because they are charismatic, but because their social lives depend on constant communication in a shifting, three-dimensional world. One of the strongest findings to emerge from that research is the existence of signature whistles — individually distinctive call types that function as learned identity signals, something very much like the individual name a dolphin goes by within its community (Janik & Sayigh, 2013).

    Social learning runs just as deep. Some dolphin foraging habits spread from one animal to another rather than through genetics — passed along socially, a rare pattern among nonhuman species (Krützen et al., 2005). Mothers and calves stay together for years, giving calves time to learn not just how to hunt, but where — which channels to follow, which bends of water hold fish (Wells, 2014).

    In some populations elsewhere in the world, dolphins even use tools — carrying marine sponges on their rostrums while foraging or trapping fish inside empty shells — behaviors that are socially learned and culturally transmitted (Krützen et al., 2005).

    That learning shapes how dolphins fit into the estuary. In many tidal systems they sit near the top of the local food web, influencing the fish communities beneath them. Yet beyond those protected waters, they are not beyond risk. Large sharks prey on dolphins, placing them within a broader coastal hierarchy where even predators can become prey (Heithaus, 2001). The role shifts with scale. The ecology remains layered.

    Two bottlenose dolphins surfacing together off Seaview Pier, N. Topsail Beach, North Carolina. Close positioning and timing are hallmarks of the complex social bonds that define dolphin societies. | Photo credit: Howard Crumpler Photography, 2026
    Two bottlenose dolphins surfacing together off Seaview Pier, N. Topsail Beach, North Carolina. Close positioning and timing are hallmarks of the complex social bonds that define dolphin societies. | Photo credit: Howard Crumpler Photography, 2026

    Dolphins are not guardians

    Popular culture has assigned dolphins a role they never chose: protector. People repeat a comforting shoreline myth — “If you’re scared of sharks, find the dolphins; they’ll protect you.” But that story is not grounded in how dolphins behave in the wild.

    Bottlenose dolphins are powerful predators. They compete, establish dominance hierarchies, and can deliver forceful blows when defending calves or asserting space. Dolphin–shark interactions occur, but they are not “rescue missions” staged for humans; they are ecological encounters shaped by risk, competition, and opportunity (Heithaus, 2001).

    Wild dolphins are also capable of injuring people. Research examining human–dolphin interactions show that close approaches — and especially feeding wild dolphins — increase the likelihood of risky contact and harmful outcomes for both dolphins and people (Cunningham-Smith et al., 2006; Vail, 2016). Over time, those interactions leave visible consequences. Long-term data from Sarasota Bay show that dolphins who have learned to associate people with food are more likely to carry injuries linked to boats and fishing gear (Christiansen et al., 2016).

    The danger is not that dolphins are “evil.” The danger is assuming they share human intentions.

    Swimming near a pod does not create a protective shield. Dolphins are not lifeguards. They are wild animals navigating their own priorities in a shared environment. Respecting that boundary is what allows coexistence.

    A bottlenose dolphin pursuing prey near a recreational vessel in a waterway in Surf City, North Carolina. Foraging behavior can bring dolphins into close proximity with boats – not as companions, but as active predators focused on fish. | Video credit: Cynthia Dirosse, 2024

    Winter dolphins

    A persistent assumption is that dolphins vanish when the water cools. In reality, seasonal distribution can be more nuanced — changing with prey, temperature, and coastal movement patterns rather than following a simple on/off presence.

    Along the mid-Atlantic coast, research shows that bottlenose dolphins shift their movements with the seasons, appearing in different areas at different times of year (Torres et al., 2005). Studies focused on estuarine dolphins in southern North Carolina document similar seasonal patterns closer to home (Silva et al., 2020). From shore, those changes can look like disappearance. But winter quiet does not always mean absence. It may simply mean dolphins are working deeper channels or less visible pathways beyond the easy reach of our eyes.

    The estuary in winter is quieter, but not empty.

    Dorsal fins in winter light off Surf City, North Carolina. Dolphins may appear less active this time of year, but changes in light, water depth, and travel corridors often influence what we notice from shore. | Photo credit: Surf City Parks, Recreation, and Tourism, 2017
    Dorsal fins in winter light off Surf City, North Carolina. Dolphins may appear less active this time of year, but changes in light, water depth, and travel corridors often influence what we notice from shore. | Photo credit: Surf City Parks, Recreation, and Tourism, 2017

    Living beside them

    Living near dolphins is a privilege — and it places us within the same waters they navigate. Vessel traffic, fishing gear, and repeated close approaches can shape the lives of animals that live for decades and raise calves slowly (Wells, 2014). Studies of dolphins that have been fed or closely approached by people show that these interactions can shift behavior, making dolphins more likely to approach boats and increasing the risk of injury and conflict (Vail, 2016). Distance, in that sense, preserves the patterns people come to watch.

    The presence of dolphins is not guaranteed. It is a sign that the system still functions — prey, water quality, shoreline structure, and the complex social knowledge dolphins carry from year to year. As long-lived predators near the top of the food web, they are indicator species, reflecting the condition of the waters they inhabit — estuary, inlet, and nearshore coast alike.

    And so when a dorsal fin rises beyond the channel markers, it means more than a moment of spectacle. It means the currents are still working, the fish are still moving, and the layered relationships that shape this shoreline are still holding.

    There is always more to learn about dolphins than fits in a single post. For those who’d like to go further, this episode of the All Creatures Podcast offers a thoughtful exploration of their biology and behavior.

    References

    Barros, N. B., Wells, R. S., & Barros, N. B. (1998). Prey and feeding patterns of resident bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. Journal of Mammalogy, 79(3), 1045. https://doi.org/10.2307/1383114

    Benoit-Bird, K. J., & Au, W. W. (2003). Prey dynamics affect foraging by a pelagic predator (Stenella longirostris) over a range of spatial and temporal scales. Behavioral Ecology and Sociobiology, 53(6), 364-373. https://doi.org/10.1007/s00265-003-0585-4

    Christiansen, F., McHugh, K. A., Bejder, L., Siegal, E. M., Lusseau, D., McCabe, E. B., Lovewell, G., & Wells, R. S. (2016). Food provisioning increases the risk of injury in a long-lived marine top predator. Royal Society Open Science, 3(12), 160560. https://doi.org/10.1098/rsos.160560

    Costa, A. P., Mcfee, W., Wilcox, L. A., Archer, F. I., & Rosel, P. E. (2022). The common bottlenose dolphin (Tursiops truncatus) ecotypes of the western North Atlantic revisited: An integrative taxonomic investigation supports the presence of distinct species. Zoological Journal of the Linnean Society, 196(4), 1608-1636. https://doi.org/10.1093/zoolinnean/zlac025

    Cunningham-Smith, P., Colbert, D. E., Wells, R. S., & Speakman, T. (2006). Evaluation of human interactions with a provisioned wild bottlenose dolphin (<I>Tursiops truncatus</I>) near Sarasota Bay, Florida, and efforts to curtail the interactions. Aquatic Mammals, 32(3), 346-356. https://doi.org/10.1578/am.32.3.2006.346

    De Robertis, A., Ryer, C. H., Veloza, A., & Brodeur, R. D. (2003). Differential effects of turbidity on prey consumption of piscivorous and planktivorous fish. Canadian Journal of Fisheries and Aquatic Sciences, 60(12), 1517-1526. https://doi.org/10.1139/f03-123

    Heithaus, M. R. (2001). Shark attacks on bottlenose dolphins (TURSIOPS ADUNCUS) in Shark Bay, Western Australia: Attack rate, bite scar frequencies, and attack seasonality. Marine Mammal Science, 17(3), 526-539. https://doi.org/10.1111/j.1748-7692.2001.tb01002.x

    Janik, V. M., & Sayigh, L. S. (2013). Communication in bottlenose dolphins: 50 years of signature whistle research. Journal of Comparative Physiology A, 199(6), 479-489. https://doi.org/10.1007/s00359-013-0817-7

    Kalahele, K. (2023, July 21). You’ve heard of facial recognition for humans, but what about dolphins and whales? Hawaii News Now. https://www.hawaiinewsnow.com/2023/07/21/uh-researchers-develop-new-face-id-technology-identify-dolphins-whales-wild/

    Krützen, M., Mann, J., Heithaus, M. R., Connor, R. C., Bejder, L., & Sherwin, W. B. (2005). Cultural transmission of tool use in bottlenose dolphins. Proceedings of the National Academy of Sciences, 102(25), 8939-8943. https://doi.org/10.1073/pnas.0500232102

    Rosel, P. E., Hansen, L., & Hohn, A. A. (2009). Restricted dispersal in a continuously distributed marine species: Common bottlenose dolphinsTursiops truncatusin coastal waters of the western North Atlantic. Molecular Ecology, 18(24), 5030-5045. https://doi.org/10.1111/j.1365-294x.2009.04413.x

    Silva, D. (2020). Abundance and seasonal distribution of the southern North Carolina estuarine system stock (USA) of common bottlenose dolphins (Tursiops truncatus). IWC Journal of Cetacean Research and Management, 21(1), 33-43. https://doi.org/10.47536/jcrm.v21i1.175

    Torres, L. G., McLellan, W. A., Meagher, E., & Pabst, D. A. (2023). Seasonal distribution and relative abundance of bottlenose dolphins, Tursiops truncatus, along the US Mid-Atlantic coast. J. Cetacean Res. Manage, 7(2), 153-161. https://doi.org/10.47536/jcrm.v7i2.748

    Torres, L. G., & Read, A. J. (2009). Where to catch a fish? The influence of foraging tactics on the ecology of bottlenose dolphins (Tursiops truncatus) in Florida Bay, Florida. Marine Mammal Science, 25(4), 797-815. https://doi.org/10.1111/j.1748-7692.2009.00297.x

    Urian, K. W., Hofmann, S., Wells, R. S., & Read, A. J. (2009). Fine‐scale population structure of bottlenose dolphins (Tursiops truncatus) in Tampa Bay, Florida. Marine Mammal Science, 25(3), 619-638. https://doi.org/10.1111/j.1748-7692.2009.00284.x

    Vail, C. S. (2016). An overview of increasing incidents of bottlenose dolphin harassment in the Gulf of Mexico and possible solutions. Frontiers in Marine Science, 3. https://doi.org/10.3389/fmars.2016.00110

    Wells, R. S. (2013). Social structure and life history of bottlenose dolphins near Sarasota Bay, Florida: Insights from four decades and five generations. Primatology Monographs, 149-172.