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FWP conducts gill net survey


December 7, 2017

Every October Montana Fish, Wildlife and Parks (FWP) conducts surveys to determine what species, and quantities are present in the Cabinet Gorge and Noxon and Thompson Falls reservoirs. This fall gill nets were set, different species were caught, and FWP as given a general idea of what is going on in our waters.

Ryan Kreiner, FWP, stated that information gathered “does not represent a population estimate, but rather a way to look at species trends over time.” Population estimates are not achievable because some species, such as “largemouth bass are not effectively sampled by the gill nets and biologists rely on data collected at bass tournaments to gauge that fishery.”

“Additionally, hundreds of trout are caught at the Thompson Falls fish ladder annually, but trout species are not regularly caught in gill nets due to the locations and time of year for gill netting,” Kreiner continued.

Kreiner shared highpoints of what was found this year.

Noxon Reservoir Walleye set an all-time high record with 51 caught. Of those, roughly 70 percent were less than 16 inches long, representing an age of 2 years. Kreiner stated this could be a result from a “strong year-class” developing from the low-water year in 2015.

Pike and smallmouth bass in Noxon Reservoir numbers declined this year. Two years ago record highs were recorded for these species.

Average sizes of largemouth and smallmouth bass have increased based off bass tournament records, there is an increase in the quantity of fish greater than 15 inches in comparison to previous years.

Not all species are thriving; the native minnow and sucker species have dramatically declined over the past 17 years according to collected data. And, for the first time ever, no peamouth were captured in the Cabinet Gorge Reservoir. Kreiner stated that this is due to the increase in non-native predators such as pike and walleye.

The most commonly captured species are yellow perch and pumpkinseed. Perch and pumpkinseed spawn and rear in habitats such as weed-beds, giving them added protection from predators. These species will serve as the main forage group with the disappearance of native forage species.

“Reproductive success of many of these typically warm-water species varies with environmental conditions, and as a result year-class strength will vary. The fishery may continue to function if no one species becomes too abundant. Harvest of walleye and pike stemming from over-abundant year-classes will actually assist with maintaining a quality fishery,” Kreiner said, summing up his 2017 gill net survey.


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