Category: Coastal Predators

  • 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

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    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

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    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/

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  • 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

  • Fish That Break the Rules: Unusual Anatomy Along the Edge of Onslow County

    Fish That Break the Rules: Unusual Anatomy Along the Edge of Onslow County

    Where Expectations Begin to Slip

    There are stretches of shoreline in Onslow County where the water looks simple.

    A low wind flattens the surface just beyond the breakers. The sand underfoot is firm, packed by a falling tide. Small schools of baitfish turn in unison at the edge of visibility, their bodies catching light and then disappearing again as if nothing had moved at all.

    From here, fish seem predictable. They swim. They are streamlined. They slip through water in ways that feel consistent, almost mechanical.

    A school of juvenile fish swim in the Surf City sound. | Photo credit: A. Mitchell
    A school of juvenile fish swim in the Surf City sound. | Photo credit: A. Mitchell

    But that impression doesn’t hold for long.

    A few steps into the surf, something crunches beneath your heel—a shell, or what remains of one.. Offshore, a shape drifts that doesn’t seem built for movement at all. In the shallows, something settles to the bottom and then, impossibly, walks.

    The closer you look, the more the pattern breaks apart. Along this stretch of coast—from the swash zone to the deeper water of Onslow Bay—some fish are not built like fish are “supposed” to be.

    And once you notice them, the rules start to feel less like rules at all.

    Teeth built for stone: Sheepshead

    The rule broken: fish are supposed to have simple teeth

    On calm mornings near New River Inlet, when the tide is just beginning to push in, the water around pilings and rock edges clears enough to see movement below the surface. Dark vertical bands appear and disappear as fish turn sideways to feed, their bodies angled tightly against pilings and rock.

    If you get a close look—often only when one is caught—you notice the teeth.

    Flat. Squared. Set in rows that look more like something borrowed from a mammal than a fish.

    Sheepshead fish have mammal-like teeth. | Photo credit: Jeannette's PIer
    Sheepshead fish have mammal-like teeth used for scraping and crushing hard shells and barnacles. | Photo credit: Jeannette’s PIer

    The sheepshead (Archosargus probatocephalus) feeds primarily on hard-shelled organisms—barnacles, oysters, mussels, and crabs attached to pilings, jetties, and natural hardbottom (Sedberry, 1987). These prey items are abundant in estuarine and nearshore environments where salinity fluctuates and structure concentrates life.

    Instead of pointed, uniform teeth, sheepshead possess incisiform front teeth for scraping and strong molariform teeth set further back for crushing (Deang et al., 2018; Hernandez & Motta, 1997). Bite force measurements and stomach content analyses show they are capable of breaking calcareous shells that would resist most coastal fishes (Hernandez & Motta, 1997).

    They are most active in waters typically ranging from 60–80°F (15–27°C), often within just a few feet of structure in depths from less than a meter to roughly 10 meters (Sedberry, 1987).

    Fish are often imagined as generalized swimmers feeding on soft prey. But along the Onslow coast, hard surfaces—oyster beds, submerged debris, pilings—create entire microhabitats built on calcium carbonate (Grabowski & Peterson, 2007).

    Sheepshead are not exceptions to the system; they are shaped by it. Their teeth are a direct response to a landscape where food remains locked inside a shell.

    Most fish don’t have teeth like this because most environments don’t require it. Here, where geology and biology meet in layers of shell and structure, the rule changes.

    The fish that walks: Bluespotted and Northern searobin

    The rule broken: fish move by swimming

    On a falling tide along the edges of Topsail Island, the water pulls thin over the sand flats. What remains is a shifting surface—ripples, shadows, and the occasional sudden burst of motion.

    Then something moves without swimming.

    It doesn’t dart or glide. It advances in short, deliberate steps, stopping and starting again, as if testing the ground before each movement.

    For a moment, it looks wrong—like something moving through air instead of water.

    The bluespotted searobin (Prionotus roseus) and the Northern searobin (Prionotus carolinus) do not rely on their fins for propulsion in the way most fish do. Instead, three detached rays from each pectoral fin extend downward, contacting the bottom and supporting the body as it moves. These rays function both as supports and as sensory structures, probing the sediment and detecting chemical cues—effectively allowing the fish to “taste” the seafloor as it moves (Bardach & Case, 1965).

    Across these shallow flats, often just inches to a few feet deep, the water warms into the upper 60s and 70s as the tide recedes. Prey is rarely exposed. Worms, small crustaceans, and buried mollusks remain hidden beneath the surface. Vision alone is not enough here. The searobin moves slowly, stepping and pausing, tracing the bottom until something beneath the sand gives itself away.

    Movement in water is usually about efficiency—minimizing drag, maximizing speed.

    But the seafloor is a different environment entirely.

    Here, visibility narrows, prey disappears beneath the surface, and swimming can carry you past what you’re trying to find. Walking—slow, deliberate, sensory-driven—becomes the better strategy.

    Most fish don’t have “legs” because most fish don’t live where walking is more useful than swimming. Along the shallow bottoms of Onslow waters, this rule no longer applies.

    The fish that swells: Northern puffer

    The rule broken: fish don’t change shape

    In late summer, when the water just beyond the breakers settles into the upper 70s, small shapes begin to move just offshore—slow, almost indifferent to the motion around them.

    One drifts closer than expected, rounded in a way that doesn’t quite match the others. It hovers, turning slightly, its movement controlled but unhurried.

    Then, without warning, the body changes.

    It expands outward, the outline swelling until the fish no longer resembles something built to move through water at all.

    The Northern puffer (Sphoeroides maculatus) does this by rapidly drawing water into a highly elastic stomach, a process that allows the body to expand far beyond its resting shape (Brainerd, 1994). Without rigid skeletal constraints like ribs or pelvic bones, that expansion can happen quickly, transforming the fish into something difficult for a predator to grasp or swallow.

    A northern pufferfish skeleton is made up of spiny modified scales (not bones) that expand like a balloon when threatended. | Photo credit: The Fossil Forum
    A Northern pufferfish skeleton is made up of spiny modified scales (not bones) that expand like a balloon when threatended. | Photo credit: The Fossil Forum

    In these nearshore waters—where predators move quickly and encounters happen at close range—there is little time to outrun what’s coming. Most fish rely on speed to escape. This one changes shape instead.

    Speed isn’t part of the solution here.

    The fish that locks itself in place: Gray triggerfish

    The rule broken: fish don’t anchor themselves

    Farther offshore, where the bottom begins to break into scattered hardbottom and reef patches, movement slows in a different way.

    Shapes hold just above the structure, adjusting position in small increments, never straying far from the surface below them.

    When disturbed, they don’t flee into open water.

    They turn downward.

    The gray triggerfish (Balistes capriscus) moves into crevices and tight spaces within the structure, where a set of dorsal spines can be raised and locked into place. The first spine lifts, and a smaller second spine holds it there—an arrangement that gives the fish its name and allows it to anchor itself firmly in place (Tyler, 1980; Lobel, 1980).

    Its body is built for this kind of movement: deep and laterally compressed, with tough, abrasive skin and strong incisor-like teeth capable of breaking into hard-shelled prey (Tyler, 1980; Lobel, 1980). These are not features meant for speed. They are features meant for contact—pressing into structure, resisting removal, holding position when movement would fail.

    In waters often 50–120 feet deep off Onslow County, where reefs and wrecks break the seafloor into pockets and edges, escape doesn’t always mean distance (Bellwood et al., 2004).

    Sometimes it means holding ground.

    Most fish survive by staying in motion.

    This one survives by becoming fixed in place, turning the structure around it into part of its defense.

    Light written into skin: Atlantic midshipman

    The rule broken: fish don’t carry light in their skin

    On warm summer nights near quiet stretches of marsh and inlet edges, the water sometimes carries sound before anything else. A low, continuous hum. It’s easy to miss unless you stop moving.

    The Atlantic midshipman (Porichthys plectrodon) produces that sound through specialized sonic muscles vibrating against the swim bladder, creating a sustained hum that can carry through shallow coastal water (Sisneros, 2009; Bass & McKibben, 2003).

    If you listen carefully during a quiet evening, the sound of a male midshipman trying to court a female might be heard. | Audio credit: SanctoSound – Integrated Ocean Observing System (IOOS)

    Along the sides of the body and across the head are rows of small organs—photophores—set into the skin, giving the fish its name and marking it as something unusual among coastal species found in these waters (Schwartz, 2013). When seen out of the water, those rows catch the light in a very particular way—small, round points that flash gold in direct sunlight, spaced with a regularity that makes them look almost set into the surface, like buttons fixed into the skin.

    The Atlantic midshipman has photophores that dazzle when out of the water, and used in seeing in darkened burrows and structures in limited light. | Photo credit: North American Native Fishes Association
    The Atlantic midshipman has photophores that dazzle when out of the water, and used in seeing in darkened burrows and structures in limited light. | Photo credit: North American Native Fishes Association

    Midshipman inhabit shallow coastal environments, often in burrows or beneath structure along muddy or sandy bottoms, typically in depths less than 20 meters.

    Light in fish is often associated with deeper water, where darkness is constant and illumination becomes necessary (Haddock et al., 2010). But along the Onslow coast, those conditions can exist in smaller, shifting pockets. Light narrows quickly with depth, suspended sediment moves with the tide, and visibility can collapse even in water shallow enough to stand in.

    Not all fish in these waters experience the bottom the same way. A flounder rests exposed on the sand, relying on camouflage and stillness. The midshipman, by contrast, spends much of its time within burrows, beneath structure, or pressed close to the substrate, where light is already limited and often disappears entirely.

    In those spaces, the rules of visibility begin to resemble something closer to deeper water, even though the surface is only a few feet above.

    The presence of photophores here does not follow the pattern most people expect.

    Not all light comes from above.

    The deep blade: Long-snouted lancetfish

    The rule broken: fish are dense, muscular swimmers

    From the beach, the horizon feels like a boundary—beyond the sandbars, beyond the nearshore currents—about two miles out, where the surface lifts just enough to hide what comes after. But beyond that line, the water doesn’t simply continue. It changes.

    Depth increases quickly. Layers begin to form. Light fades long before the bottom is reached.

    And in those deeper waters off Onslow Bay, some fish are not built to chase anything at all.

    The long-nosed lancetfish lives in the middle depths of the ocean where body density is less desirable for a drifting fish. | Photo credit: ML – some rights reserved (CC BY-NC)
    The long-nosed lancetfish lives in the middle depths of the ocean where body density is less desirable for a drifting fish. | Photo credit: ML – some rights reserved (CC BY-NC)

    The long-snouted lancetfish (Alepisaurus ferox) lives in the midwater column, often hundreds of meters below the surface. Its body is long and thin, almost blade-like, with muscle reduced and tissue that is less dense than most active predators, appearing almost soft in the water (Drazen & Seibel, 2007).

    It does not move with the steady, powered swimming most fish rely on. Instead, it drifts, adjusting position and taking prey as it comes within reach. Stomach analyses show a wide range of prey—fish, squid, and even other lancetfish—suggesting opportunism rather than pursuit (Kubota & Uyeno, 1970).

    In these deeper layers, energy becomes harder to acquire and more costly to use.

    Building and maintaining dense muscle comes at a cost. Chasing prey demands more of it (Sutton, 2013).

    Here, that balance shifts.

    The lancetfish represents a different solution—one that reduces the cost of movement and relies instead on encounter.

    Most fish are built to swim.

    This one is built to wait.

    The armored survivor: Atlantic sturgeon

    The rule broken: fish are supposed to have scales

    In cooler months, when water temperatures drop into the 50s and 60s, large shapes move along the bottom of estuaries and nearshore waters.

    They do not flash or turn sharply. They move steadily, close to the sediment.

    At times, that movement reaches the surface. A back breaks through, arcing briefly before slipping under again, the shape unfamiliar enough that it doesn’t immediately read as a fish.

    The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) retains an older form—rows of bony scutes instead of the flexible scales seen in most fishes (Bemis et al., 1997). Along the underside, a protrusible mouth extends downward, drawing in prey from the bottom through suction rather than pursuit (ASSRT, 2007; Bemis et al., 1997).

    An anadromous fish, they move between river systems and coastal waters, passing through estuaries and along the nearshore edge, often in depths ranging from shallow channels to over 100 feet offshore (Dunton et al., 2015; ASSRT, 2007).

    This design is not new. It has persisted for tens of millions of years, carried forward through changing coastlines, shifting sea levels, and the rise of entirely different groups of fishes (Bemis et al., 1997).

    Atlantic sturgeon have a bony structure that has remained relatively unchanged for millions of years. | Photo credits: mdadswell – some rights reserved (CC BY-NC) (left); Steven McGrath – some rights reserved (CC BY-NC-ND) (right)

    It works because the conditions it responds to have never fully disappeared.

    Along the bottom, prey remains buried. Sediment still shifts with current and tide. Feeding still depends on contact more than speed. Armor still protects a body that cannot easily maneuver out of danger.

    For a long time, these fish seemed to fade from local waters. In Onslow County, encounters became rare enough to feel like absence. But populations have persisted elsewhere, and in nearby systems like the Cape Fear River, they are being observed again with increasing frequency—moving through channels, returning to spawning grounds, reappearing in places where they had not been seen in years (Dunton et al., 2015; ASSRT, 2007).

    Their range has shifted before. It may be shifting again.

    What remains constant is the need for connection—between river and ocean, between spawning grounds and feeding habitat.

    This fish does not depend on a single place. It depends on the continuity between them.

    Not all designs are meant to change. Some persist because the system they belong to still exists.

    The drifting giant: Ocean sunfish

    The rule broken: fish are supposed to be shaped for swimming

    Occasionally, especially in warmer months when currents shift, something appears offshore that barely seems to move at all.

    A large, flattened body. A fin breaking the surface. Then another, held there longer than expected.

    It drifts more than it swims.

    At times, it lingers there, tilted at the surface, absorbing the sun before slipping back beneath the water.

    The ocean sunfish (Mola mola) is one of the heaviest bony fish, reaching weights over 1,000 kg. Its body is truncated, lacking a true caudal fin, and propulsion is achieved through synchronized movements of dorsal and anal fins (Pope et al., 2010; Watanabe et al., 2009).

    After diving into colder, deeper water, sunfish often return to the surface, where this slow, drifting posture allows their body temperature to rise again (Watanabe et al., 2009). Prolonged time at the surface can leave the skin visibly altered—shifting from darker grey to lighter tones, sometimes appearing pale or pinkened under sustained exposure.

    Sunfish often inhabit offshore waters but can approach nearshore areas following currents and prey, particularly gelatinous organisms like jellyfish (Cartamil & Lowe, 2004).

    By most expectations, this body plan shouldn’t work.

    But it does—because efficiency, here, takes a different form. It is about buoyancy, drift, and feeding on abundant, slow-moving prey.

    In a system where jellyfish blooms are seasonal and sometimes dense, a fish shaped like this becomes not an anomaly, but a specialist.

    Answers to a layered environment

    From the shoreline, the water still looks simple.

    Small waves rise and fall. Baitfish turn and vanish. The surface holds its shape.

    But beneath that surface, the rules have already begun to shift.

    Fish move through these waters in ways that don’t match what we expect—crushing shell, stepping across the bottom, changing shape, holding themselves in place, carrying structures that catch light, drifting where others would swim, or moving through forms shaped long before this coastline took its present shape.

    What appears, from the beach, to be a single environment is something else entirely. It is layered—sand, structure, depth, temperature, light—each one asking something different of the animals that live within it.

    And the fish that seem unusual are not exceptions.

    They are answers.

    A layered system, at New River Inlet, seen from the surface. | Photo credit: A. Mitchell
    A layered system, at New River Inlet, seen from the surface. | Photo credit: A. Mitchell

    References

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    Bardach, J. E., & Case, J. (1965). Sensory capabilities of the modified fins of squirrel hake (Urophycis chuss) and Searobins (Prionotus carolinus and P. evolans). Copeia, 1965(2), 194. https://doi.org/10.2307/1440724

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