The Bering Sea, a vast and productive marine environment situated in the northernmost Pacific Ocean, often brings to mind images of frigid waters and abundant fisheries. Its unique geography, featuring both a deep Aleutian Basin and a shallow continental shelf, supports a rich diversity of marine life, from numerous fish species to marine mammals and seabirds. A common question arises regarding whether sharks, creatures typically associated with warmer ocean habitats, can thrive in such a cold and formidable expanse.
Confirmed Shark Residents
Sharks do indeed inhabit the cold waters of the Bering Sea. The most prominent species found here are the Pacific sleeper shark and the Greenland shark. The Pacific sleeper shark, Somniosus pacificus, is a large deep-water shark, typically dark gray to black, that can reach lengths of about 4.4 meters (14 feet) but might exceed 7 meters (23 feet).
Another significant resident is the Greenland shark, Somniosus microcephalus, a thickset species with a short, rounded snout and small eyes. While the Pacific sleeper shark is often considered the largest shark in Alaskan waters, the Greenland shark can also grow to an impressive size, rivaling its Pacific counterpart. Salmon sharks (Lamna ditropis) are found in the Bering Sea. Pacific spiny dogfish (Squalus suckleyi) are also present.
Surviving the Cold: Unique Adaptations
The sharks of the Bering Sea exhibit remarkable adaptations that allow them to thrive in near-freezing temperatures. Both the Greenland shark and the Pacific sleeper shark possess high concentrations of urea and trimethylamine N-oxide (TMAO) in their tissues. These compounds act as osmoprotectants, helping to maintain water balance and prevent cell damage in the cold, high-pressure environment, while TMAO also counteracts the protein-destabilizing effects of urea.
These species also have a notably slow metabolism, which conserves energy in an environment where food can be scarce. This reduced metabolic rate contributes to their sluggish movement, with Greenland sharks, for instance, swimming at an average of only 0.34 meters per second. The Pacific sleeper shark’s liver oil, unlike that of many other sharks, does not contain squalene, which would solidify in cold temperatures. Instead, its liver contains low-density compounds that remain fluid, aiding buoyancy. Salmon sharks, in contrast, are endothermic, meaning they can maintain a body temperature warmer than the surrounding water, which allows them to hunt effectively in cold waters.
Their Place in the Ecosystem
Sharks in the Bering Sea occupy important positions within the marine food web. Pacific sleeper sharks and Greenland sharks function as apex predators and scavengers. Pacific sleeper sharks prey on a variety of organisms, including bottom fishes, octopuses, squids, and even marine mammals like seals and sea lions. Their ability to consume carrion also plays a role in nutrient recycling in the deep-sea environment.
Greenland sharks are known to consume fish, seals, and even large land mammals that fall into the water, such as reindeer or polar bears. Their presence helps regulate prey populations and contributes to the overall balance of the ecosystem. Salmon sharks are primarily pelagic, inhabiting offshore and coastal areas, and undertake migrations based on prey availability.