Arctic Science Journeys
Radio Script

shark photo

Large and in charge: Salmon sharks have several rows of razor-sharp teeth they use to catch schools of migrating salmon, herring, pollock and other fast-moving fish. Scientists estimate salmon sharks in Prince William Sound eat more than two million pounds of fish each summer. (Photo courtesy NMFS)

Shark Invasion

INTRO: By now, most of us have heard about some of the ecosystem changes occurring in Alaska. Our climate is getting warmer, Steller sea lion populations are in trouble, and salmon runs are faltering, to name but a few. But one change some people might not have heard about is the dramatic increase in the number of sharks roaming Alaska waters. Before you go for a swim, listen to this week's Arctic Science Journeys Radio with Doug Schneider.

STORY: If near-freezing water isn't enough to keep you from taking a dip in the Gulf of Alaska, perhaps the idea of sharing the sea with thousands of sharks will keep you safely on shore. Bruce Wright is an ecologist who studies sharks for the National Marine Fisheries Service. He says Alaska is experiencing a shark population explosion.

WRIGHT: "Just a case in point: In one of our study areas, which is about ten square miles, in a little port in northern Prince William Sound called Port Gravina, we had an aerial survey a couple of weeks ago and we counted just at the surface 2,000 salmon sharks. That's just part of Port Gravina. If you go to Port Nellie Juan to the west, and some of the other areas locally, there's that many sharks again in all those other bays, and all the way down to Hinchinbrook Entrance, too."

The sharks showing up in places like Kodiak, Cook Inlet, and Prince William Sound, are salmon sharks—so named because they feed on migrating salmon. While they aren't known to attack people, they are the closest living relative to the great white shark, of Jaws fame. An average salmon shark grows to about 8 feet long, weighs around 400 pounds, and has a voracious appetite.

WRIGHT: "If you take just these 2,000 sharks in this ten-square-mile area, for the three months that they are in there—using what we know about their energetics—those sharks would need about two million pounds of salmon to survive. That's probably what they consume."

Wright and other researchers have been studying salmon sharks in Prince William Sound for the past three years. They've tagged hundreds of sharks in an effort to learn more about where they go and how they may be altering the North Pacific Ocean's food chain.

WRIGHT: "Being top-end predators, it doesn't take many of them to have an impact on their prey base. Now we're seeing just thousands of these fish in this region, and so I know that they're probably restructuring this ecosystem. I'm real interested in the shark's relationship to these changes. Why has it happened? What's going to happen? Who are they eating? When they run out of that food, what are they going to eat next?"

Wright says salmon sharks may be responding to the abundance of salmon in Alaska waters, helped by hatcheries and warmer water temperatures that have improved both shark and salmon survival.

WRIGHT: "I think by creating this food patch and by there being so many salmon around, that it's promoted salmon sharks to use the area."

Scientists believe that up to two million salmon sharks may inhabit the western North Pacific, and that some of these sharks may have followed migrating salmon back to Alaska.

OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.

Thanks to the following individuals for help preparing this script:

Bruce A. Wright, Executive Director
Conservation Science Institute
P.O. Box 823, Santa Cruz, CA 95061
Phone: 831-439-9432

Lee Hulbert, Fisheries Research Biologist
NOAA National Marine Fisheries Service
11305 Glacier Highway
Juneau, Alaska 99801
Phone: 907-789-6056

Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.

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More audio clips:

Listen in as scientists collect data from a thrashing shark! (0:57)


Open and say ah

Fish out of water

Related websites:

Salmon Shark Facts

Alaska Shark Assessment Program