Radio Script
1999

__________________

The Case for Forage Fish
__________________

Don't have RealAudio player? Download free software.

INTRO: Alaska's Prince William Sound has long been a haven for seals, salmon and bears. One researcher says that's because the sound is host to abundant schools of small prey fish called forage fish. Doug Schneider has more on this week's Arctic Science Journeys.

STORY: Look down upon Alaska's Prince William Sound on just about any clear day in May or June, and the ocean appears to have come down with a mild case of the measles.

Spots resembling ink blotches dot the water near the shoreline. They shimmer and change shape under the glint of the sun. Yet the sound isn't sick. These spots are in fact a sign of a healthy ecosystem. They are schools of herring, sand lance and other juvenile fish rising to feed on the billions of nearly microscopic plankton hatching on the surface.

BROWN: "What we're looking for are schools which stand out as little dark spots. Some are irregular shapes, some are little dark circles and balls."

That's Evelyn Brown--a fisheries researcher at the University of Alaska Fairbanks. She's come to Prince William Sound each of the last three years to study the herring, sand lance, capelin and other forage fish--so called because they are preyed on by larger fish, seabirds and marine mammals.

BROWN: "They're the underdogs out there. Everything eats them. They're incredibly interesting. The schools are really beautiful--they wheel and turn like a flock of shorebirds. The schools have that kind of beauty to me."

Using an airplane, she's able to survey the sound quickly. Herring tend to school in nice circles--easily identified from the air. Sand lance, she says, swim unpredictably.

BROWN: "The sand lance are really different. They're very irregularly shaped. They're generally much closer to shore. There's a huge range of school sizes, but they're generally larger, more elongated. They can be crescents, ovals, snake shapes. And they are either a solid in color or translucent gray depending on how thick the school is. They don't sparkle like a herring school and they don't seem to have as many birds associated with them."

Evelyn Brown says finding the schools is just the first step. Understanding how forage fish interact with their environment and with predators such as larger fish, seabirds and marine mammals is more difficult.

BROWN: "We're looking for areas where there's not only schools occurring but also how many there are, how close they are to each other. What's the geographic range--are they inshore or offshore? Are they associated with a particular marine habitat?"

Using planes to find fish isn't new--fishermen have been doing it for years. What's unique is that she used aerial photography and underwater cameras mounted on boats to follow hundreds of forage fish schools. Evelyn Brown's video and photographs show schools of herring darting for safety as auklets, kittiwakes and other diving seabirds plunge into the school.

BROWN: "We also as a surprise captured images of puffins feeding on the schools, and of coho salmon feeding on sand lance. A lot of the sand lance schools were associated with salmon. You'd see the school go by and then you'd see the salmon go by."

The sound's feeding frenzy is triggered by the annual hatch of tiny crustaceans, called zooplankton. When that happens, schools of fish, sometimes thousands of tons, swarm to the surface to feed. Besides scientists, seabirds also seem to recognize the shapes.

BROWN: "Bird biologists are telling me this--and we're seeing it--that a lot of these schools that are being fed on by the white birds, the gulls and kittiwakes, are also being preyed on by diving birds. And the diving birds come together and drive the school up to the surface and at that time they are available to the gulls."

Evelyn Brown's study had other notable findings. She confirmed, for example, that herring seem to be the most important food for seabirds and marine mammals in the sound. She also discovered that forage fish tend to use the same areas for feeding and spawning each year.

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

Evelyn Brown, Research Associate
Institute of Marine Science
University of Alaska Fairbanks
907-474-5801
ebrown@ims.uaf.edu

If you'd like more information about the forage fish and Prince William Sound, check out this website:

http://www.pwssc.gen.ak.us/sea/sea.html