Portuguese dogfish and cookiecutter sharks have both been reported around 3,700 meters. There is no solid evidence for sharks living in the deepest trenches, and chemical constraints may explain the apparent limit.
At a glance
- Reported shark limit
- ~3,700 m
- About 12,100 feet below the surface.
- Record species
- At least two
- Portuguese dogfish and cookiecutter shark records reach this depth.
- Deep trenches
- No sharks
- Verified records do not extend into hadal depths.
The record is shared
A review of fish colonization in the deep sea identified the Portuguese dogfish and cookiecutter shark as the deepest-recorded sharks, both at approximately 3,700 meters. A trawl capture, camera observation and vertical movement by a tagged animal do not answer exactly the same ecological question, so “deepest caught” and “deepest resident” should not be used interchangeably.
A surprisingly shallow ceiling
Bony fishes have been documented thousands of meters deeper. The absence of sharks from abyssal and hadal fish communities is therefore not simply a lack of fish food or sampling. Researchers have proposed that the chemistry sharks use to balance urea in their tissues becomes limiting as pressure rises.
Pressure meets biochemistry
Sharks retain urea to keep their body fluids near seawater’s osmotic concentration. Trimethylamine N-oxide, or TMAO, helps counteract urea’s destabilizing effect on proteins and also increases with depth in many marine animals. Models suggest the required chemical balance may reach a physiological ceiling for chondrichthyans near their observed maximum depth.
Why records can change
Deep-sea sampling is sparse, and many records come from fishing gear that integrates a range of depths. New tags and remotely operated vehicles could refine the limit or identify another record holder. A future observation somewhat below 3,700 meters would update the number; it would not automatically erase the broader pattern separating sharks from trench-dwelling bony fishes.
CHECK THE EVIDENCE