Lake trout in Hidden Lake: What's their present status?

Posted: Friday, April 29, 2011

Hidden Lake is a popular area for recreation on the Kenai National Wildlife Refuge. It offers great activities such as camping, hiking, and fishing and is easily accessed by the Skilak Lake Loop Road from two points on the Sterling Highway. Hidden Lake is most notorious for its popular Lake trout fishery, which is the largest sport fishery for Lake trout on the Kenai Peninsula.

U.s. Fish And Wildlife Service Photo
U.s. Fish And Wildlife Service Photo
Lake trout with external gray tag near the base of the dorsal fin.

Lake trout are widely dispersed throughout Alaska and North America and, contrary to what some may believe, they are actually a char and not a trout. Taxonomically, this means their observable characteristics are more similar to Dolly Varden and Arctic char than to rainbow trout or salmon.

Lake trout spawn in the fall and typically inhabit cold, deep lakes that have low nutrient levels and are rich in dissolved oxygen. Lake trout have slow growth rates, low reproductive capacity, and females usually spawn in alternate years. Most Lake trout do not become sexually mature until they are between 5 and 10 years old, and males often mature at smaller sizes than females. These intricate life-history characteristics and restrictive habitat requirements make Lake trout vulnerable to overharvest. This is why many Lake trout fisheries are managed conservatively throughout Alaska.

Within the past few years, anglers and management biologists have become concerned about the health of the Lake trout population in Hidden Lake. The primary reason for this concern is the decrease in reported harvest and catch of Lake trout in Hidden Lake over the past decade. The decrease in harvest can be somewhat attributed to changes in the sport fishing regulations that decreased daily bag limits.

However, catch has also declined over this same period which indicates these declines could be an artifact from several years of high harvest rates. These high harvest rates occurred over 20 years ago which makes their present day effects difficult to measure, but they have likely impacted the population in Hidden Lake in some way.

The primary problem for management biologists is that very little information is known about the population dynamics of Lake trout in Hidden Lake, particularly the numbers of mature fish and how much harvest this fisheries can sustain. Assessment of this fishery is limited to a few creel surveys conducted during the early 1990s by the Kenai Field Office of the U.S. Fish and Wildlife Service, and annual Statewide Harvest Surveys administered by the Sport Fish Division of the Alaska Department of Fish and Game. To ensure that this important Refuge population does not decline below levels necessary to support a sustainable fishery, the Kenai Field Office has initiated the first of two studies with goals of understanding the life-history and population dynamics of Lake trout in Hidden Lake.

In the first study, we are hoping to identify spawning areas, and describe the distribution and movements of mature Lake trout greater than 18 inches. The Kenai Field Office will accomplish this by tagging fish with radio transmitters. Tagged fish will be tracked weekly by boat during the spring and summer months, and more frequently during the fall spawning season.

Once the spawning areas have been identified, the next task will be to determine if we can capture fish in the spawning areas to conduct a mark-recapture abundance estimate of mature fish. The mark-recapture study will require knowledge of spawning locations and movements of Lake trout among spawning areas. In addition to the telemetry work, the Kenai Field Office is also collecting data on length and weight of sampled fish. These data will allow us to estimate the harvest potential for Lake trout in Hidden Lake.

Recently, the Kenai Field Office tagged 22 Lake trout with cooperative anglers who were ice fishing on Hidden Lake during March. Tagging will be initiated again in May once the lake ice retreats. Anglers can identify a tagged fish by the presence of an external gray tag near the base of the dorsal fin. This external tag has a unique five digit number (e.g., #22642) followed by a telephone number. If you happen to catch one of these fish, please return it to the water and call the toll-free number on the tag and report the tag number, date, and location.

If you would like to participate in the study or just want to learn more about our project, call Ken Gates at the Kenai Field Office at 1-800-822-6550.

Ken Gates is a fishery biologist at the Kenai Fish and Wildlife Field Office in Soldotna (http://alaska.fws.gov/fisheries/fieldoffice/kenai/index.htm). For more detailed information about the Kenai National Wildlife refuge, you can check the refuge website at http://kenai.fws.gov or on Facebook at http://www.facebook.com/kenainationalwildliferefuge



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