Invasive fish threaten Kenai: Fish and Game biologists discover northern pike in Hall Lake

Posted: Monday, August 16, 2010

How many northern pike are required to populate an entire habitat?

Photo Courtesy Alaska Department Of Fish And Game
Photo Courtesy Alaska Department Of Fish And Game
A photo provided by the Alaska Department of Fish and Game shows a 31-inch northern pike caught recently on Hall Lake near the Kenai River in Sterling.

"It only takes one male and one female," said US Fish and Wildlife biologist Doug Palmer.

Department of Fish and Game Sport Fish biologist Robert Begich said that the invasive fish has been newly discovered in a lake connected to the Kenai River. He did not know how the pike came to be in Hall Lake, located near Soldotna, but suspected illegal stocking.

The species is native to northern and western portions of the state, according to the department's pike management plan, but wasn't brought to the Peninsula until the mid 70s. The voracious species can devastate local salmon populations, prompting the sportfish division began an outreach campaign to let fishermen know about the effects of pike infestations in 1997.

According to Begich, the department will check if water runs between the lake's outlet creek and the river year round, but his department is uncertain at this time.

"It's possible that juvenile [pike] could leave the system," said department biologist Rob Massengil.

After leaving four nets in the lake overnight, an investigating team caught two pike: one approximately 31 inches, and the other 28 inches. Massengil tends to think it's a small population based on the netting results.

He spotted a pike boating around the lake during the initial survey. The team didn't find any juvenile pike, Massengil said, which lends him to believe the invasive fish haven't been spawning.

Pike usually appear in landlocked lakes as a result of illegal stocking, the biologists said. But in a open lake, such as Hall, it's possible that the species spread from another water source, known or unknown. Massengil said that the fish eating predator could spread to a salmon breeding ground from the current lake, as well.

"It's even scarier when you have an open lake like Hall," he said.

John Toppenberg, who lives near the lake, said he noticed a fish taking prey in the lake during early June. He said that he saw a dorsal fin when it turned underwater, which made him suspect it was a pike.

He reported the invasive species to an acquaintance who worked for U.S Fish and Wildlife recently when he bumped into her at the grocery store. Fish and Wildlife forwarded the report to the Department of Fish and Game.

Another resident, Steve Mussman, said that a dead pike floated by his boat when he and his son were watching the loons in the early August. The search reminded him of an incident last summer when he saw a man cleaning fish by the lake. The carcasses struck him as unsual.

"Looking back, I think they were pike given the skin color," Mussman said.

He didn't report either sighting.

Palmer said that cameras in the watershed monitor the number of pike entering the Kenai. Three pike have entered the river since the program began two years ago, but he's not sure how long the pike have been there.

The Kenai's sparsely vegetated waters aren't an ideal habitat for pike, according to the biologist. He's more concerned about the fish establishing themselves in the deliberate Moose River, a breeding ground for 20 to 40 percent of the Kenai system's coho salmon.

Pike hide in dense plants and wait for prey to swim by. Juvenile salmon and trout are an easy food source, which meams infestations near breeding streams can do harm to the ecosystem and local economy.

Palmer said that there are several ways to mitigate pike infestations. Netting lakes can remove smaller groups of pike, but chemicals such as rotenone are used with larger populations. He said that rotenone blocks a fish or amphibian from intaking oxygen through their gill system.

The chemical process is efficient for landlocked ponds and lakes. It becomes a more strenuous undertaking when an affected waterbody is connected to an existing system because rotenone suffocates any water-breathing creature. Palmer said that water stations need to be set up along the stream to neutralize the chemical before it affects non-invasive species.

Massengil said that draining lakes works on smaller lakes and man-made ponds, but doesn't consider that a realistic option for Hall.

However, the department has no set plans as of yet. It's only begun an investigation.

"I need more time on the water," he said.

Tony Cella can be reached at tony.cella@peninsulaclarion.com.



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