Cutthroat trout surveys help track population trends in Priest Lake

by Rob Ryan, IDFG Regional Fisheries Biologist

PRIEST LAKE, Idaho — Idaho’s state fish, the cutthroat trout, is a staple in many of the state’s major drainages. The westslope cutthroat subspecies were once widely abundant in North Idaho’s large lake systems where they spawned in tributary streams and grew large in the lakes.

Although cutthroat once dominated angler catch in the Panhandle’s large lakes, they are no longer the primary species. Harvest of westslope cutthroat trout in waters such as Priest Lake was upwards of 4,000 fish per year in the 1950’s, but declined to hundreds of fish by the 1980’s. Fish and Game biologists say the diminishing catch rates were the result of declining fishing effort and fish populations, changing fish communities and impaired tributary spawning habitats.

Fishery managers concerned about the populations responded by restricting harvest opportunities to rebuild populations. Today, westslope cutthroat represent one of the most abundant species in many spawning tributaries around Priest Lake, but little is understood as to why they are so abundant. Though cutthroat anglers aren’t as numerous as they used to be, those  who target them for catch and release say fishing is not too bad.

In an effort to better understand current and future cutthroat populations in Priest Lake, Idaho Fish and Game (IDFG) developed a monitoring strategy first implemented in 2014. Fisheries staff sampled cutthroat throughout Priest Lake in late spring using short gill nets designed to catch multiple sizes of fish while targeting trout and reducing the catch of non-trout species by using floating nets.

The gill nets weren’t intended to provide an estimate of the total number of cutthroat in the lake, but rather an index of their abundance. The index of abundance in this case, measured as fish per net, can then be used to compare the population from year to year as well as from lake to lake.

In their first sampling effort IDFG caught an average of two cutthroat per net with consistent catches throughout Priest Lake. While that information alone is of limited use, when collected over multiple years and or paired with results from similar surveys on other lakes this information will be quite valuable for understanding the number and health of this population.

Cutthroat collected in this survey were in the six to eighteen inch range.

Fish and Game is continuing to study this population and present data about what they learn from the project and how the information gained will provide angling opportunity for the public.

To learn more about fisheries in the Panhandle Region, go to fishandgame.idaho.gov and look up the Panhandle Fisheries Newsletter. Regional Fishery Manager Jim Fredericks compiles the information annually to provide information on local fisheries projects and programs for anglers.

Fredericks also produces a electronic newsletter. For more information call (208)769-1414 or email jim.fredericks@idfg.idaho.gov.