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Biologists use radio for tracking rainbows

Posted: Thursday, September 28, 2000

SOLDOTNA (AP) -- Five years of study already has proved the Kenai River's rainbow trout are tough enough -- they've got battle scars -- to thrive despite the annual attack by anglers skilled and not so skilled.

With the aid of small transmitters embedded in 200 fish this fall, biologists hope to shed more light on these plucky and highly prized predators. For instance, where do they spend the long winter, and what role do the big lakes Kenai and Skilak play in their lives?

A crew of six anglers hired by the state Department of Fish and Game inserted the last of the pencil-thin radios recently. They spent a month and a half using fly- and spinning rods to catch fish between Kenai and Skilak lakes, where the blue-green Kenai winds through stands of spruces and alders and drops through dramatic rock-walled canyons. They caught a great number of fish in the 18- to 26-inch range, said Jeff Breakfield, a state biologist leading the team.

''It's beautiful,'' he said recently. ''The sun burned through the other day. We saw brown bear, moose, eagles -- all sorts of stuff. It's one of the best jobs around, definitely.''

But it's not all fun, he said. ''We had to stop fishing and put transmitters in these fish.''

Anglers already have hooked a few of them and phoned Fish and Game to find out why the trout were trailing foot-long wires. It's a radio antenna.

Calls like that give Breakfield a chance to check his crew's work.

Each fish was sliced open near the anal fin so the transmitters could be inserted. Crews used a dissolving thread to close the wound. Word from the anglers is that the radio-tagged rainbows, characteristically, are healing well, he said.

State and federal biologists say they'll spend the next three years -- the life of the transmitter batteries -- monitoring these rainbows by boat, car and plane to see where they feed and spawn and where they winter.

Rainbows are residents. They eat salmon eggs and the flesh of spawned-out salmon in bountiful summer. Then some retreat to Kenai and Skilak lakes for the long winter while others hunker down in the Kenai River.

Biologists say they want to verify at least one theory that could explain what now seems like a staggeringly high catch rate of rainbows.

Annual harvest surveys indicate anglers hook and release some 50,000 Kenai River rainbows a year. Biologists aren't sure how many rainbows live in the upper Kenai, but it could be as few as 5,000. That would mean that on average a single rainbow could get hooked as many as 10 times a year.

Physical evidence suggests many these fish are repeat customers. About 90 percent have battle scars on their lower jaws, he said.

''If our population estimate is correct, which we're not sure of, we've got a fishery that's got an average hook and release per fish higher than anything we can find worldwide for rainbows,'' said Bruce King, a state biologist leading the research.

But the population estimate may not be correct. Is something else going on that's throwing off the numbers? The radio tracking could help biologists find out.

Biologists believe thousands of rainbows linger in Kenai and Skilak lakes all summer, jetting into the river system only in August and September, when the river is plugged with the carcasses of spawned-out salmon.

Guides report easily catching lots of rainbows this time of year that are more silvery, not the trademark rainbow color, King said. Lake-dwelling fish retain those silver markings.

If a significant number of radio-tagged fish remain in the lakes most of summer, then it could back up the theory that there are more rainbows in the river system than thought.

Radio tracking is the latest installment in a series of cooperative federal and state studies since 1995 that have targeted rainbows and Dolly Varden char in the upper Kenai and its tributaries.

This testing was funded largely through a $42,000 grant from Kenai River Sportfishing Inc., an angler advocacy and habitat protection group. The money paid for the transmitters.

A chief goal of this study is to find out how many upper Kenai rainbows spawn each spring in the Russian River, a legendary fish-rich tributary.

It's easy to count trout in the clear-running and shallow waters of the Russian, which leads some biologists to hope the system may one day offer them a way to estimate the size of the entire population, King said. If radio tracking shows that a predictable fraction of rainbows spawn in the Russian, a biologist could walk the bank, get a head count, then do some fast math and have a ''quick and dirty'' assessment of the whole population, King said.

Tracking the rainbows ultimately will help resource managers adjust regulations without making a critical misstep that could harm the fishery, he said.

''When we get to the (Alaska Board of Fisheries), we'll have the ability to discuss issues like season dates, whether we should be trophy fishing or allowing a harvest,'' he said. ''Radio studies typically can answer a variety of questions. Our hope is this one will allow us to both check existing information and put it into some context.''



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