Sharks inhabit Alaskan waters. While less commonly associated with warmer climates, Alaska’s diverse marine environment supports several species. These creatures have adapted to the region’s frigid conditions, playing an important role in the marine ecosystem.
Shark Species in Alaskan Waters
Alaskan waters are home to several notable shark species, primarily the Pacific sleeper shark and the salmon shark. The Pacific sleeper shark (Somniosus pacificus) is a large, deep-water species, typically measuring 3.65 to 4.4 meters (12 to 14.5 feet) in length, though some individuals reach over 7 meters (23 feet). This shark has a dark gray to black coloration, a cylindrical body, and a short, rounded snout.
The salmon shark (Lamna ditropis) is another prominent species, characterized by its dark blue-gray to black body with a white, often blotched, underside. It possesses a short, conical snout and resembles a smaller great white shark. Salmon sharks can grow up to 3 meters (10 feet) long and weigh over 450 kilograms (992 pounds), with average sizes around 2 to 2.5 meters (6.5 to 8 feet). This species is known for its powerful swimming ability and active nature.
Alaskan Shark Habitats and Adaptations
These sharks inhabit the North Pacific, including the Gulf of Alaska and the Bering Sea, preferring continental shelves and slopes. Pacific sleeper sharks typically reside in deep waters, ranging from the surface down to 2,000 meters (6,600 feet), though they can be found in shallower coastal areas in northern latitudes. Salmon sharks are pelagic, found from the surface to depths below 152 meters (500 feet), thriving in cold boreal to cool temperate waters.
Pacific sleeper sharks exhibit a slow metabolism, which conserves energy in the deep waters they inhabit. Their livers contain low-density compounds that ensure buoyancy and maintain fluidity in frigid temperatures. Additionally, they possess high concentrations of urea and trimethylamine oxide (TMAO) that act as cryoprotectants, preventing ice crystal formation within their tissues.
In contrast, salmon sharks are endothermic, a rare trait among fish, allowing them to maintain a body temperature warmer than the surrounding water, sometimes up to 15.6°C (28°F) above ambient. This ability is facilitated by a countercurrent heat exchange system called the rete mirabile, which warms blood returning from muscles. This physiological advantage enables faster muscle contractions, enhancing their speed and agility in cold water for hunting prey like Pacific salmon, herring, pollock, and squid. Pacific sleeper sharks are opportunistic predators, consuming bony fish, crustaceans, mollusks, and marine mammals.
Understanding the Risk to Humans
Encounters or attacks by sharks in Alaskan waters are rare. There have been no reported fatal shark attacks in Alaska. The shark species found in these waters are not considered a significant threat to humans.
This low risk is due to the natural behavior and habitat preferences of these sharks. Pacific sleeper sharks typically inhabit deep waters, far removed from human recreational activities, and their naturally sluggish demeanor means they are unlikely to interact with people. Salmon sharks, though powerful and active, are not known to be aggressive towards humans, focusing instead on their natural prey sources. While some reports of unusual injuries on marine mammals suggest shark interactions, direct incidents involving humans are uncommon. Encounters are often linked to mistaken identity or interactions with fishing activities.