By Jenny Neyman
Invasive northern pike have been served with an eviction notice at Stormy Lake north of Nikiski, to be enforced this fall if the Alaska Department of Fish and Game’s application for a pesticide use permit is approved by the Alaska Department of Environmental Conservation. Once pike are gone, native fish species will be invited back home.
The permit is up for public comment through 4 p.m. Feb. 23. Comments may be submitted by mail to Rebecca Colvin, 555 Cordova St., Anchorage, AK 99501. To view the application, visit www.dec.state.ak.us/eh/pest/publicnotice.htm. For more information, call 269-7802 or email Rebecca.Colvin@alaska.gov.
Fish and Game has prepared an environmental assessment on the Stormy Lake project, as well. To view that document, visit http://www.adfg.alaska.gov/static/species/nonnative/invasive/rotenone/pdfs/stormy_lake_ea.pdf. Comments on the environmental assessment may be submitted be email to firstname.lastname@example.org, by mail at 43961 K-Beach Road, Suite B Soldotna, AK 99669, or by calling Robert Massengill, fishery biologist, at 262‐9368.
If approved, Fish and Game plans to treat Stormy Lake with the pesticide Rotenone sometime in August or September. The lake would be closed to public access during the treatment and the following cleanup period, with signage warning people away from the water.
“Once treatment is completed, we would discourage drinking the water or swimming until the Rotenone fully deactivates, we’re anticipating two to six weeks after the treatment,” said Robert Massengill, fishery biologist with Fish and Game.
Pike are native to much of Alaska and many areas of the Lower 48, and as big, active, tough fish, they’re a lot of fun to catch. Anglers’ affinity for pike is thought to be the way they spread from their native range into Southcentral Alaska. Pike penetrated into Alaska from Russia when the state was still glaciated. They settled into regions north and west of the Alaska Range, where they don’t cause many problems. They evolved along with other fish species. The other species developed predator-avoidance abilities.
Pike are notoriously voracious eaters, preferring soft-finned salmonids, like salmon, Dolly Varden and rainbow trout, but also eat sticklebacks, leeches, insects or most anything else they can get their sharp, tooth-laden jaws around. They live in shallow, still, weedy water. In Bristol Bay, and other regions with native pike populations, the lakes tend to be large and deep. Pike stick close to shore while other fish, especially pike’s preferred meal of juvenile salmonids, can rear in deeper water.
But in Southcentral, lake topography is different and the fish inhabiting those lakes aren’t used to having pike around. Big, deep lakes like Kenai, Skilak and Tustumena aren’t the main concern, because pike and other species can avoid overlapping habitat. Pike are a bigger problem in the many smaller, weedier lakes that dot Southcentral.
The Southcentral pike invasion was first recorded in Bulchitna Lake in the Susitna River drainage in 1950. From there they spread throughout much of the Susitna drainage, eating their way through rearing salmon populations. Pike were introduced on the Kenai Peninsula in the mid-1970s, first to Derk’s Lake in the Soldotna Creek drainage. They’ve been confirmed in seven of the eight lakes in the Soldotna Creek drainage, in lakes as far south as the Tote Road area south of Soldotna, and as far north as Stormy Lake north of Nikiski. Fourteen Kenai Peninsula lakes have confirmed pike populations, and there have been 18 lakes with pike detected in them at one point or another.
In their 30 years on the peninsula, pike have significantly impacted fish populations. In the Soldotna Creek drainage, netting of the lakes has come up with few fish other than pike.
In Stormy Lake, pike were detected around 2001. Angler catch estimates from before then showed a robust rainbow fishery, and the lake was known as having the best Arctic char fishing on the peninsula. Nowadays, catch estimates have plummeted. Even the size and number of pike caught have decreased, a sign that the fish have decimated their available food supply.
“The take-home message for Stormy Lake is we’ve (Fish and Game) spent quite bit of time out there the last couple of years. It’s pretty obvious the wild rainbow trout and Arctic char populations have collapsed as a result of northern pike,” Massengill said.
All it takes is one pair of a reproducing male and female to start a pike population, and they are tenaciously difficult and expensive to eradicate once established. Simply targeting them for fishing — whether through netting, hook and line, spears or any other methods — isn’t enough.
Stormy Lake is at the top of Fish and Game’s pike hit list, in part because pike have decimated the resident fish species, and because Stormy could be a corridor to a much larger invasion. The lake drains via a small creek into the Swanson River, a highway connection through 240 square miles of drainage. The area is a veritable Swiss-cheese, lake-studded wetlands area linking to the Swan Lake and Moose River systems.
Currently there’s a net barrier strung across the drainage creek, but it’s not guaranteed to keep pike contained to the lake. High-water events could swamp the net, and tiny eggs or larval pike could get through the mesh.
Fish and Game contracted with an engineering firm to research possible methods for containing and eradicating pike, and public meetings were held May 13, 14 and 25, 2011, in Nikiski and Kenai, for attendees to enter their comments and concerns into public record.
The two leading options were draining Stormy Laky, done by drilling and installing a pipe from the bluff about 1,000 feet away and draining it underground or by pumping water out overland. It’s estimated that it would take five years for the lake to refill.
Fish and Game’s preferred option, and the least expensive — which Fish and Game has already used successfully on Arc and Scout lakes — is treating Stormy Lake with the chemical Rotenone.
Rotenone is a plant-based product that does not penetrate soil to get into groundwater, degrades quickly in the environment, does not bioaccumulate and is not shown to pose health risks to people or other mammals at the concentrations Fish and Game would use. The Environmental Protection Agency states that there is no human health concern to infants and children — the most at-risk populations — from exposure to Rotenone at 40 parts per billion. Fish and Game would apply it in a concentrated form at 40 ppb to 50 ppb, but it would dissipate quickly below that level once in the water. Fish and Game would recommend closing public access to the lake during treatment, as a precaution.
Fish are vulnerable to the chemical because of a thin membrane layer on their gills that allows Rotenone to absorb easily. Other species, like mammals, don’t have the same absorption route.
Fish and Game would capture and relocate native aquatic life, such as fish and freshwater clams, and later return them to the lake. Some creatures, like worms, bugs, zooplankton and aquatic invertebrates, wouldn’t be able to be relocated. But Massengill has said that studies of previously treated lakes show that those creatures are not permanently harmed by the application of Rotenone. They actually have been shown to thrive after treatment, since the dead fish act as a fertilizer for the smaller creatures.
“We’ve put a lot of effort into trying to collect, for brood-stock purposes, what’s left of the Arcic char population so we can rear some of their offspring in a hatchery and reintroduce them to the lake before we lose that population,” Massengill said. “Besides the char we would collect representative fish of all the species in the lake, from long-nose suckers and sticklebacks to the rainbows and chars, and hold them in a safe lake during the treatment, then return them. So we have a plan to help kick-start the native fish assemblage.”
Massengill estimates it could take several years before there’s a viable fishery — for species other than pike — in Stormy Lake again. But without eradicating the pike, he predicts the other fish species will never repopulate the lake on their own.
Fish and Game’s next target in its continued fight against invasive pike on the peninsula is the Soldotna Creek drainage. Massengill said Fish and Game will hold public scoping meetings on that project sometime this winter or spring, probably in March.