Sharks of Onslow County
December hushes the coastline of Onslow County. The marshgrass stiffens in the cold, the surf stills between storms, and the New River Inlet carries the metallic stillness of early winter. Yet beneath that calm, the water hums with motion — tiny pulses, ripples, and vibrations that weave a hidden holiday soundtrack, a kind of underwater sleigh bells rung in pressure waves.
Sharks, lingering along the nearshore troughs or cruising the outer edge of the estuary, sense these disturbances with remarkable clarity. Every mullet tail-beat, crab scuttle, and sediment shift radiates through the water as a low-frequency pressure wave. In the quiet of December, these signals travel farther and cleaner, strengthened by winter’s denser water, slower prey, and reduced turbidity (Mickle & Higgs, 2021; Mogdans, 2019).
To sharks, these vibrations form a map, a three-dimensional winter soundscape that reveals direction, distance, and urgency (Montgomery, Baker & Carton, 2000; Montgomery et al., 2000). And layered beneath these hydrodynamic cues, the faint electric fields produced by the heartbeat and muscle activity of nearby prey glow through the water, detectable at nanovolt precision (Anderson et al., 2017; England et al., 2021).
This “music” is not metaphor — it is the sensory world sharks inhabit, sharpened by the very conditions winter imposes.
Cold water shifts the physics of survival. As temperatures fall, prey metabolism slows, creating weaker and more irregular movement patterns — the exact low-frequency signatures sharks detect most easily (Sisneros & Rogers, 2016). Reduced plankton and sediment yield a clearer path for particle motion, allowing hydrodynamic cues to propagate farther through the winter water column (Mogdans, 2019).
This turns the estuary into a rich field of vibrations. Fish schooling tightly create rolling displacement waves. Crabs shifting beneath the sand produce intermittent pulses. Even subtle fin flicks produce particle motion detectable by sharks’ sensory systems (Maruska, 2001).
Winter looks barren to us.
To sharks, it resonates.
The shark’s lateral line is a mechanosensory canal system tuned to detect water displacement in the exact frequency range produced by struggling fish and crustaceans (Montgomery, Baker & Carton, 2000). Neuromasts within the canal encode both direction and amplitude, transforming low-frequency motion into a spatial map of nearby activity (Mogdans, 2019).
In December, this system excels:
Even acoustic cues — particle motion at frequencies under ~300 Hz — become part of this integration. Sharks are most sensitive to these low-frequency bands, enabling discrimination of movement types in murky or dark winter water (Poppelier et al., 2022).
To a shark, each pulse is information.
Each ripple is direction.
Each vibration is a bell rung underwater.
Watch how sharks use their lateral line system to sense ripples and vibrations long before they see their prey. | Video courtesy of National Aquarium – “Sharks Lateral Line”
When a shark closes the final distance, tracking transitions from vibration to electricity. The Ampullae of Lorenzini detect microvolt-scale electric fields emitted by the body of every living animal. Sensitivity thresholds fall into the tens of nanovolts per centimeter — among the most refined biological detection limits known (Anderson et al., 2017; Newton, Gill & Kajiura, 2019; England et al., 2021).
Electroreception enables sharks to:
Classic electroreception work demonstrated these capacities decades ago, and modern experimental studies in hammerheads confirm high-resolution electro-sensitivity during close-range hunting (Kajiura & Holland, 2002; Kalmijn, 2000).
In winter, when storms churn the sediment and twilight comes early, this sense becomes even more essential.
Sharks do not need light — they follow electricity.
Video courtesy of PBS Deep Look, illustrating how sharks use electroreception to locate prey invisible to sight or sound.
Picture a December evening at the New River Inlet. The ebb tide pulls cold water from the sound toward the ocean. A juvenile Atlantic sharpnose shark glides along a shallow bar, guided not by sight, but by the underwater vibrations pulsing through its lateral line.
A faint, uneven pressure wave reaches the shark — the hydrodynamic signature of a mullet slowed by the cold (Montgomery et al., 2000). The shark turns. Another pulse follows, the rhythm revealing both direction and weakness.
Within a few body lengths, electric cues rise above the hydrodynamic noise. The Ampullae of Lorenzini detect microvolt-scale oscillations from the mullet’s buried body (Newton, Gill & Kajiura, 2019; England et al., 2021). One quick strike completes the hunt.
This is winter’s choreography:
vibrations at a distance,
electricity up close,
all woven seamlessly through still December water.
Although prey slow in winter, sharks must continue to feed. Their dual sensory systems allow efficient predation in the season that challenges most marine animals. These abilities help sharks:
Even as water temperatures drop, species like Atlantic sharpnose sharks, bonnetheads, and offshore Atlantic spiny dogfish remain active, relying heavily on the interplay of hydrodynamic and electroreceptive cues (Maruska, 2001).
Winter is not lifeless.
It is a sensory masterclass.
While we celebrate the holidays with sleigh bells, carols, and glowing lights, the Atlantic hums with its own winter rhythms. Sharks navigate December through vibrations, particle motion, and faint electrical fields — signals older than any tradition and tuned to the pulse of life beneath the cold.
Their bells are not made of metal.
They are made of motion.
Of electricity.
Of the quiet echoes of survival beneath the tide. These are the Shark Sleigh Bells, ringing softly beneath Onslow County’s winter waters.
Anderson, J. M., Clegg, T. M., Véras, L. V., & Holland, K. N. (2017). Insight into shark magnetic field perception from empirical observations. Scientific Reports, 7(1). https://doi.org/10.1038/s41598-017-11459-8
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Poppelier, T., Bonsberger, J., Berkhout, B. W., Pollmanns, R., & Schluessel, V. (2022). Acoustic discrimination in the grey bamboo shark Chiloscyllium griseum. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-10257-1
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