Sunday, June 24, 2012

Alaska's Lake Monster?: a large shark moving into fresh water could be answer

Big Foot.  Nessie.  Many regions of the world have there local monster animal legends.  Persistent folklore often invites the curiosity of scientists who wish to determine once and for all what is fact and what is fiction.  They do so because of the belief that where there's smoke there just might be fire.

In Alaska, at Lake Lliamna, there were rumors of a monster lurking about in the dark cold water. Scientists had debated the possibility that a Pacific sleeper shark, or sharks, had entered the lake. There had been anecdotal sightings of what could possibly have been a sleeper shark but there has not been any definitive, scientific proof.

This past Wednesday, a reported sighting of a sleeper shark in a similar, nearby lake has added some additional weight to the theory.  As reported in the Alaska Dispatch, "Chris Babcock of King Cove, Alaska, spotted something in the shallow water of the King Cove Lagoon, a lake of brackish water. Closer inspection revealed a Pacific sleeper shark rolling and thrashing around. The shark's antics were filmed and posted on YouTube (see video below)According to Babcock, the fish approached him when he entered shallow water, but later moved to deeper water." 

The shark's behavior was considered a bit unusual - but perhaps not.  That is to say, there is a lot that marine experts don't know about these sharks.  They can reach a length of 20 feet and weigh upwards of 4 tons.  That's a big shark by any standard.  In addition to being predators, they are thought to be major scavengers, clearing the ocean bottom of dead animals as they sink into the cold depths, but sleeper sharks caught accidentally in nets have also been found to have other freshwater fish including salmon in their stomachs.  Hence, the possibility that sleeper sharks are able to venture into freshwater or brackish lakes, perhaps drawn in by the opportunity to feed on large freshwater fish.

But how long can they survive in freshwater?  Is there a pattern or migratory cycle to their appearances in lakes?  Is it seasonal, based on weather or temperature changes, or are they following the migratory or breeding patterns of other prey species?  Scientists like Bruce Wright of the Aleutian Pribilof Island Association would like to answer those questions by tagging and tracking sleeper sharks, as is done with other shark species worldwide.

Some marine scientists think that sleeper sharks could become a major predator in Arctic waters due to climate change.  With warmer water temperatures melting greater amounts of sea ice, animals like seals and polar bears are spending more time in water.  Some caught sleeper sharks have been found to have seal and even polar bear remains inside, so this slow-moving predator - that catches its prey with a strong vacuum motion of its large mouth, biting with its teeth to get down what it couldn't swallow whole - could have an impact of the balance in the Arctic ecosystem.

Is the Pacific sleeper shark the "lake monster" of Alaskan folklore?  Seems reasonable enough.  The closely-related Greenland shark has been put forth as a candidate for Scotland's Loch Ness resident sea monster, so perhaps someday we will have definitive proof that monsters do exist.  They just might end up a bit tamer than our imaginations have conjured up over the years.

Source: Alaska Dispatch

1 comment:

Christine B.Osborne said...

As to what this shark may have been doing, I suggest it could have been trying to throw off, to rid itself of sea lice, or other parasite. As for it eating a polar bear, hmm. A cub, maybe...