Priest Lake trout population to be scrutinized

SANDPOINT — The Idaho Department of Fish & Game is conducting a comprehensive study of lake trout in Priest Lake to help guide the development of a long-term management plan for the lake’s sport fishery.

The project comes in the wake of rigorous debate about long-term management of the lake’s sport fishery.

Fish & Game is teaming up with the University of Idaho’s College of Natural Resources and the Kalispel Tribe to estimate the number of lake trout, in addition to drawing out key characteristics such as growth and survival rates and food habits.

To capture trout for the population estimate, large-scale commercial netting vessels, similar to the ones used on Lake Pend Oreille, will be used. From March to May, deep-water trap nets and short-duration gill net will be used to capture, measure and mark lake trout with individually numbered tags.

As many marked fish as possible will be released unharmed, although Fish & Game said a small number of lake trout would be sacrificed for age and stomach analysis.

The research project is the beginning of an effort to develop a more complete understanding of the lake’s fishery and its relationship to zooplankton, kokanee and Mysis shrimp.

Historically, upper and lower Priest lakes were popular sport fisheries for native cutthroat trout and bull trout. Kokanee were introduced in the 1930s and ’40s, which provided an abundant food source for bull trout. However, kokanee became the most popular sport fish, supporting a harvest of 50,000-100,000 and 15,000 angler days per year.

The trio of fisheries last through the 1970s, but abruptly collapsed the following decade, when the introduction of Mysis shrimp caused the lake trout population to explode, according to Fish & Game.

Millions of kokanee fry and hundreds of thousands of cutthroat fingerlings were stocked in Priest Lake and its tributaries in the 1980s in an attempt to overcome the predator impact of lakers.

But fishery biologists said those efforts were unsuccessful.

The fishery shifted from a diverse yield and trophy fishery to one dominated by lake trout. Though that was fine with some anglers, Fish & Game said overall participation declined by a third to a half since the 1950s even though the area’s population tripled over the same period.

The average size of lake trout declined over the years as anglers targeted lake trout and the prey base disappeared. Fish & Game implemented a variety of regulations in response to the declining size of lakers, but they had little impact.

Tagging studies, meanwhile, indicated the decrease in size structure was a function of poor growth rates rather than harvest, Fish & Game said.

Angler opinions about management direction on Priest have been split since the collapse of the kokanee population in the late 1970s. Some angler would prefer to see restoration of a cutthroat, bull trout and kokanee fishery, while others would like to see the lake managed for lake trout. Yet more pin hopes on the idea that a balance between kokanee and lake trout is feasible.

Fish & Game said the lake trout population estimate will be a tremendously valuable piece of information regardless of the management direction for the lake. The department anticipates scheduling a public hearing in late February to discuss the project and answer questions anglers may have.