Fish and Game tackles invasive species problem

Northern pike have overrun several lakes on Kenai Peninsula

Posted: Sunday, October 18, 2009

Oct. 13 was a bad day to be a pike in Scout Lake.

M. Scott Moon / Peninsula Clarion
M. Scott Moon / Peninsula Clarion

Actually, it was a bad day to be any kind of fish living in the small lake just south of the Sterling Highway between mileposts 85 and 86.

Crews from the Department of Fish and Game descended on the lake on Tuesday wearing hazardous material suits and toting big cylinders of the piscicide rotenone around the lake in department boats.

According to Robert Begich, the sportfish area management biologist for Fish and Game in Soldotna, Scout has had northern pike since at least 2004.

The slender, arrow shaped predator fish with a toothy maw, was first reported by children who live and fish nearby.

Pike are native to Alaska, but not southcentral.

They came here through what some biologists refer to as "bucket biology," the illegal transplant of non-native fish into a new body of water.

When pike are dumped into ecosystems that haven't evolved with the hungry fast breeding fish as part of the food chain, they wreak havoc in short while.

"They insert themselves into the forage base and eat it out of house and home," Begich said.

Pike will eat just about anything they can get their mouths around, and have been known to feast not just on other fish, but even small rodents, baby birds, reptiles and amphibians where available.

In lakes like Scout, which have been stocked as far back as the 1950's, pike will start by consuming the other fish.

Once they've depleted that food source, they move on to insects and invertebrates, eventually turning to cannibalism.

The end result, Begich said, is a sad picture where only a few large fish survive, or the population is stunted.

This is a particularly chilling picture given the proximity to other waterways supporting wild pacific salmon.

Pike have overrun several lakes on the peninsula, but Fish and Game has been working to reclaim them, starting with "landlocked" lakes such as Scout, and Arc Lake in Soldotna, which was successfully treated last year.

On Tuesday, crews applied rotenone in different sections of the lake, both in powder and liquid form.

The chemical is a plant derivative that's easily absorbed through the gills of aquatic organisms.

The toxic compound prevents the fish from absorbing oxygen, and as crews worked, the first victims were surfacing belly up.

Begich said rotenone has been widely used across the country for fisheries management, and has no known public health impacts.

While the fishing is guaranteed to be off in Scout for at least a year, the lake will continue to be safe to recreate in for people and pets, so long as your pets don't have gills.

Begich said this is the third time the chemical has been applied in the lake since the early '60's.

Previous applications were meant to control the stickleback population, a small forage species that was believed to be eating the stocked rainbow fry.

Fish and Game will continue to monitor the concentration of rotenone in the lake on a weekly basis through the rest of the fall and into next summer.

Begich said the chemical degrades in sunlight, and while ice-up will extend its potency; it should be gone by the beginning of the summer.

Along with the chemical treatment, Fish and Game also has gill nets in the water to monitor whether if any pike are surviving.

"If we determine the lake is pike free, it will be restocked as soon as the summer of 2010," Begich said.

Fish and Game discontinues stocking programs in lakes that have confirmed pike populations.

The program is designed to produce high yield fisheries, but with pike around, Fish and Game would just end up feeding the invaders and not the anglers, Begich explained.

Since people have put pike into Scout and other area lakes, Begich said Fish and Game considered whether there was interest in a pike fishery and held public meetings on the matter several years ago.

"There's been overwhelming support for their eradication," he said.

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