UPDATE: Check out the comments section for more information regarding Greenland sharks in St. Lawrence Seaway and maximum weight recorded for a Greenland shark. Thanks to Jeffrey Gallant of GEERG.
An article from the Alaska Dispatch presents a theory suggesting that lake monsters, such as those that have been reportedly sighted at Loch Ness and Alaska’s Lake Iliamna, could be large sleeper sharks, like the Greenland shark (Somniosus microcephalus) or Pacific sleeper shark (Somniosus pacificus). The article’s author, Bruce Wright, notes the documented presence of Greenland sharks in the St. Lawrence Seaway as providing credibility to the theory of sleeper sharks being able to survive in freshwater.
Pacific sleeper sharks are known to inhabit the waters around Alaska, and it has been suggested, by some, that Greenland sharks might be inhabiting the United Kingdom’s waters. Both species are believed to be able to reach maximum lengths of over 20′, and Wright believes these large sleeper sharks might be the key to explaining “lake monster” sightings at Loch Ness and Lake Iliamna.
Wright plans to lead an expedition in hopes of documenting the presence of a sleeper shark in Alaska’s Lake Iliamna later this year.
For more information, check out the Wright’s sleeper shark theory article.