Subsistence and sports fishermen across much of Alaska prize the northern pike. But in Southcentral Alaska, pike are a threat to salmon populations. The Cook Inlet Aquaculture Association (CIAA) works in partnership with other organizations to safeguard salmon from invasive pike in the Cook Inlet area.
Northern pike in Alaska
Pike are native all over the northern hemisphere, including north and west of the Alaska Range. To the south of the Alaska Range, pike are an invasive species, which means a nonnative species that causes or is likely to cause economic or environmental harm or harm to human health.
Pike thrive in fresh and brackish waters. They prefer vegetated, low flow, shallow habitats where they can easily hide and dart out to ambush prey. They are voracious hunters, known to eat smaller fish, insects, frogs, small birds, and rodents.
Pike were illegally introduced into Bulchitna Lake in the Susitna Watershed in the 1950s. Since then they have spread throughout the watershed and further into the Kenai Peninsula.
What’s the problem with Northern pike in Southcentral Alaska?
In their native range, pike have coexisted for thousands of years with other native species. For example, pike coexist with the world’s largest sockeye salmon population in Bristol Bay. The bay’s large drainages allow salmon to take advantage of deep lakes and fast running streams to avoid pike.
Southcentral Alaska is full of shallow, weedy habitat. For 11,000 years, these areas have been home to juvenile salmon and trout in the absence of pike. When pike invade these habitats, salmon and trout cannot escape to deeper refuge to hide from the invading predators. Coupled with the fact that pike prefer juvenile salmon over other prey, many salmon populations in Southcentral Alaska are vulnerable to northern pike.
Since its introduction, pike have spread to over 150 systems in Southcentral Alaska. Northern pike have totally replaced once-thriving salmon populations. One example of this was at Alexander Creek where invasive pike wiped out a popular Chinook salmon fishery.
How does CIAA help stop invasive pike?
CIAA conserves and improves salmon habitat because these habitats are important for ensuring future runs regardless of a salmon’s origin in a hatchery or in the wild. Invasive species work is part of our habitat program.
CIAA has monitored juvenile and adult salmon throughout the Susitna watershed. Over the years, we noticed changes in lakes that had northern pike populations. Starting in the mid-2000s, we started investigating northern pike impacts to several lakes.
With the result of those initial studies in hand, we began to focus on Shell, Chelatna, Whiskey, and Hewitt lakes — all of which are or were significant producers of sockeye salmon. At Shell Lake, we are trying to save the native population. Pike and other contributing factors nearly eliminated these fish. We have been using intensive harvesting, combined with the use of our Trail Lakes Hatchery to reintroduce native salmon to Shell Lake.
An ongoing effort: Northern pike will never be gone
Due to the interconnectedness of the Susitna watershed, complete eradication is not an option, but we know that suppression of pike populations helps salmon populations. At Chelatna, Whiskey, Hewitt, and Shell lakes, we have harvested over 20,000 pike to keep the population down.
Lead CIAA biologist, Andy Wizik, estimates 2.25 million more adult salmon may have returned to these lakes by removing the pike. This estimate takes into account that each pike removed ate at least one juvenile salmon. The number could be much higher when you account for the pike we’ve seen with bellies full of baby salmon.
We are currently harvesting northern pike at Whiskey, Hewitt, Shell, and Chelatna lakes through 2023. Much of CIAA’s northern pike work is supported by grants and we work with partners such as the Alaska Department of Fish and Game and the University of Alaska Fairbanks.
Working to stop the spread and impacts of invasive species is one way CIAA helps provide salmon fisheries.
