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Setnetters: Please help stop Northern pike

For more than six decades, Northern pike has harmed salmon runs in the Cook Inlet. ADF&G is asking for your help to stop them.

by | May 31, 2023


You may be familiar with the issue of invasive northern pike decimating regional fisheries. Pike are native to Interior and Western Alaska waters but were not naturally found in Southcentral. This changed decades ago when an angler illegally introduced pike from the Fairbanks area to a lake in the Yentna River drainage.

Sixty years later, pike are now prevalent throughout the Mat-Su, Anchorage, Tyonek/ Beluga, and formerly, parts of the Kenai Peninsula. Overall, northern pike have been confirmed in over 150 waters, mostly from their slow spread through open river systems.

Aquatic apex predators

Northern pike are top predators in aquatic ecosystems, so this invasion has come with significant costs, both ecologically and economically. Impacts from pike vary by habitat. In ideal habitats in worst case scenarios, pike can eat all the fish in a lake and end up the only species left.

Pike thrive in shallow, weedy, interconnected, and low flow waters, and unfortunately, there is a lot of this pike-friendly habitat in Southcentral. Here, pike predation can forever change these ecosystems. In deep lakes or high-velocity glacial rivers, this tends not to be the case as pike don’t spawn, rear, or feed in these habitats so there is little interaction between pike and salmonid prey. 

A threat to the Kenai

The northern Kenai Peninsula is an area of greatest concern regarding pike invasions due to its remoteness and suitable pike habitat. Twenty years ago, pike had established populations in dozens of lakes on the peninsula.

Years of concentrated efforts by Alaska Department of Fish and Game (ADF&G) and partners to eradicate them have been successful, and barring any undetected remnants, the Kenai Peninsula is currently considered pike-free for the first time since the 1970s. Besides the ever-present concern that pike would be illegally reintroduced here, another perilous pathway for their introduction has emerged.

The Cook Inlet corridor

In recent years, it has become evident that pike use Cook Inlet as a corridor to access new waters. This may be surprising. Yet, in their native range in Scandinavia, pike are well documented to occur and spawn in estuaries. Over the years, there have been reports of set netters encountering pike in northern Cook Inlet. In 2019, the first of these Cook Inlet-caught pike was turned into ADF&G.

Shortly after, pike were discovered in Miller Creek within the Kenai National Wildlife Refuge near Point Possession. During surveys to confirm the presence of pike in the drainage, one female pike was caught that was substantially larger than the rest. The ear bone (otolith) was removed and analyzed for chemical signatures, which indicated the fish swam through the saltwater before entering Miller Creek. We believe this is a smoking gun, and sufficient evidence to  determine pike established via migration through Cook Inlet. 

Eradicated in Miller Creek

Due to rapid response work from ADF&G, CIAA, U.S. Fish and Wildlife Service, the Kenai National Wildlife Refuge, and the Kenai Watershed Forum, the Miller Creek pike population is no more. However, two new pike populations in Anchorage have now emerged in Campbell Lake and East and West Chester Lagoons. Otoliths analyzed from pike in both systems also suggest they were established via migration through Cook Inlet. Another population, near Tyonek, is also believed to have invaded the same way. Angler reports suggest pike are also moving through the Knik Arm. These systems would be devastated if pike became established. 

Salt water survivors

Last spring ADF&G conducted salinity tolerance experiments with pike and learned that they can survive multiple days in salinities representative of Cook Inlet north of NIkiski. This new information about Cook Inlet as a pathway to northern pike invasion is very concerning to management agencies and organizations. Collectively, managers are trying to develop ways of preventing pike from accessing highly vulnerable habitats, especially those on the northern Kenai Peninsula to keep it pike-free.

This is where we need your help! If you happen to encounter a pike in your setnets, we ask that you retain that fish whole and bring it to your closest ADF&G office at your earliest convenience before it deteriorates.

Each one of these fish is a piece of the puzzle on how, when, and where pike are using Cook Inlet. Also, if you or anyone you know is fishing in your local lakes and find a pike in a place you’ve never seen one before, please retain it and report it right away to: Invasive Species Reporter, Alaska Department of Fish and Game or call 1-877-INVASIV.  

Thank you! Your help with this is greatly appreciated!

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