Conservation of native salmonids in South-Central Alaska

Science Center Objects

The proliferation of introduced northern pike in Southcentral Alaska is an urgent fishery management concern because pike are voracious predators that prey heavily on juvenile salmonids. Eradication of pike is not possible in connected freshwater networks, so managers must develop control methods that reduce pike populations to less destructive numbers. We are using field and bioenergetics modeling approaches to develop quantitative tools that will allow managers to characterize the impact of pike predation on salmonid productivity, to prioritize habitats that need pike control, and to assess the effectiveness of pike control efforts on salmonid productivity. In addition, we are also testing several technologies for controlling introducing pike, including the NEPTUN electric barrier.

USGS scientist Adam Sepulveda sits with a sample of invasive northern pike in south central Alaska.

USGS scientist Adam Sepulveda sits with a sample of invasive northern pike in south central Alaska.Public domain

Northern pike (Esox lucius) are an extremely valuable food source and sport fish in their native waters of Western Alaska and the interior north of the Alaska Range. However, outside of their native range these fish drastically reduce species populations such as native fish, waterfowl, wood frogs, small mammals and also threaten wild and stocked fisheries. Northern pike were introduced to the south-central and southeast regions of Alaska in the 1950’s and are considered an invasive species. Specific areas of impact are the Susitna watershed, Matanuska valley, Anchorage area and Kenai Peninsula.

Currently, northern pike are found in over 130 small lakes and streams in the Cook Inlet area most likely gaining access and establishing a stronghold in the Susitna River drainage through illegal stocking. The Susitna River drainage covers tens of thousands of square miles, and contains a myriad of shallow lakes, sloughs and clear water tributaries, many of which are prime northern pike spawning and rearing habitats. Once established, northern pike have been shown to be especially devastating to juvenile salmonids, and have significantly impacted numerous Coho and Sockeye salmon runs from the Susitna River drainage. The presence of northern pike in the Susitna River drainage poses a threat to other south-central Alaska streams because it could be a thoroughfare to other salmon populations in the region.

The establishment of northern pike threatens local, national and international economies as salmon are valuable commodities and pike are able to push out salmon populations over time potentially impacting the Kenai Peninsula economy which is dependent on revenue generated from wildlife viewing, commercial and recreational fisheries. Salmon and rainbow trout are also a main food source and are culturally important to many of the Inuit tribal peoples of Alaska.

The primary control methodologies to reduce invasive pike in Alaska utilize the chemical application of the common fish pesticide rotenone, which is found in limited supply, is costly to apply, and only a few applications are feasible annually due to the magnitude of the pike infestation. To respond to the limited control options, new methodologies are being tested that integrate suppression management techniques targeting various life history stages of pike. These innovative methods could assist land managers in the conservation of salmon in the Kenai Peninsula and surrounding areas.

The USGS Northern Rocky Mountain Science Center is exploring the use of and testing of commonly applied methodology, along with new technological approaches to control and eradicate northern pike for the conservation of native salmonids in South-Central Alaska.