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SCIENCE! Alaska's Sharks


Assuming you have a TV and don’t live under a rock (the later would probably preclude you from reading this article anyway) you know that last week was Shark Week on Discovery Channel. I’ll refrain from any rants on the ridiculousness that was Megalodon or how SyFy did a more honest job with their campy shark horror movie Sharknado. I did however want to spend some time talking about sharks in Alaska.
Most people don’t associate Alaska with a thriving shark population; sightings here are rare outside of the seasonal migration of salmon sharks in areas like Prince William Sound.
Don’t let that fool you, Alaska is home to plenty of sharks. We have three dominant species here: salmon sharks (Lamna ditropis), spiny dogfish (Squalus suckleyi), and Pacific sleeper sharks (Somniosus pacificus). Parts of Southeast Alaska have also played host to the occasional white shark (Carcharodon carcharias), which are more prevalent in the warmer waters off the California coast.
According to the Florida Museum of Natural History, the scientific name for salmon shark Lamna ditropis is translated to mean “voracious with two keels”. They have high dorsal and caudal fins that help them navigate and turn as they attack in bursts. As their common name suggests, their diet is built heavily around predating on salmon (especially during the annual runs) but they can also be pretty opportunistic as well.

Pacific sleeper sharks are the real deep sea monsters of the Alaska coastline. Very little is known about the biology and ecology of Pacific sleepers, but they are generally classified as a demersal (deep sea) species. They are often caught in commercial by-catch, particularly in long line fisheries that target deep bottom dwelling schools of black cod and demersal rockfish taken at depths of several hundred fathoms. They are incredible beasts to behold, and I have had the opportunity to witness some impressive specimens being hauled up from the murky depths of Chatham and Clarence Straits.

 Photos of Pacific sleeper sharks caught during ADF&G Longline Surveys near Angoon Alaska.

Finally we have the spiny dogfish. These sharks are generally smaller (2 to 3 and a half feet in length) and more unassuming than their more notable cousins.
They are very slow growing and as such can live to be 100 years old. Their gestation period is approximately 24 months long and the females give birth to about 9 pups at a time. There used to only be one species designation for Atlantic and Pacific populations of spiny dogfish, but they have recently been split into two genetically unique species with similar biological and ecological niches.
During the last Alaska Board of Fisheries cycle, there were proposals to explore the commercial harvest of spiny dogfish. Many commercial fishermen feel that their numbers are growing in Southeast Alaska. They are already being captured as by-catch in increasing numbers, and the fishermen felt like opening them up to a “test” fishery would be a good way to assess their real numbers, explore their market value, and depress their numbers enough to reduce incidental by-catch (as well as reduce their predatory effects on target species).
Sharks are prevalent enough in Southeast Alaska to have found their way in to Tlingit culture. The Wooshkeetaan clan of the Xunaa Kwáan (Hoonah and Glacier Bay area) has the shark as their primary crest, and numerous other clans include it as a secondary crest.

 Map Courtesy of Alaska Native Knowledge Network

Sharks have been a hot topic in the news, not just because of Shark Week, but because of concerns over increased numbers and the likelihood of increased attacks. Populations of white sharks off Massachusetts to as far north as Maine have come under recent scrutiny in the policy arena. Meanwhile, California white sharks are believed to be on the verge of extirpation.
The population boom is believed to be supported largely by the increase of marine mammals, which are thriving once again thanks to careful management and protections granted through the Marine Mammal Protection Act (MMPA). The MMPA has also been under scrutiny here in Alaska, where it has fostered the reintroduction and dramatic increase of sea otters, particularly in Southeast Alaska.
Sen. Bert Steadman proposed an otter bounty program during the last legislative session as a way of appeasing concerns that sea otters were destroying commercial shellfish fisheries (but that’s another story for another time).
Alaska IS home to sharks, but most of them are not the massive predators portrayed in popular media venues like Shark Week. I’m not aware of any person in Alaska ever getting bitten, and could find no records to that effect. That doesn’t mean they’re any less impressive or exciting. I was truly amazed at the size and strength of a rolling Pacific sleeper shark as it tossed and tangled its way around a large circle hook. And if you really want to live on the edge, you can always go to Cordova and charter a kayak fly fishing adventure for salmon sharks. Feel free to share your own personal shark stories and images in the comments below!