Kokanee stocked for the first time in CJ Strike Reservoir

Fishing at southern Idaho's CJ Strike Reservoir will soon get a bit more interesting thanks to the recent stocking of 90,000 hatchery kokanee fingerlings. Known for its crappie, perch, bass, and trout, a unique set of circumstances led to this first-ever addition to CJ Strike in 2020.

Each fall, Fish and Game staff collect and fertilize eggs from spawning wild kokanee in the Deadwood River. This program provides all of the hatchery-reared early run kokanee for the state of Idaho. Due to variation in egg survival within the hatchery, excess eggs are collected to ensure that enough young kokanee survive to meet release numbers. When hatching rates exceed expectations, a surplus of kokanee fingerlings results. These "bonus" fish must be stocked out in early spring to free up rearing space for the remaining fish to grow to the appropriate size prior to their scheduled releases later in the spring.

Most years, these surplus kokanee are stocked in traditional kokanee waters to help supplement those fisheries. For example, in 2019, the Department stocked 150,000 surplus kokanee into Arrowrock Reservoir and 200,000 surplus into Lucky Peak Reservoir in an effort to boost those fisheries. However, starting in 2020, Fish and Game fisheries research staff are initiating a study to evaluate the size-at-release of kokanee fingerlings. This study will compare survival rates of stocked three-inch long kokanee fingerlings (the traditional size) with those that are four inches long. Larger kokanee are known to survive better as they are better at avoiding predators after stocking. However, fewer of these fish can be reared and stocked because bigger fingerlings take up more hatchery space. This study will determine if releasing fewer, larger fingerlings ultimately provides more adult fish for anglers compared to releasing more, smaller fingerlings.

Due to the intricacies of this important study (study fish need unique marks and must be released at certain sizes), this year's surplus kokanee were not eligible to be stocked in the majority of existing kokanee waters. This led biologists to consider alternate waters that traditionally haven’t been stocked with kokanee. Enter CJ Strike Reservoir! Fish and Game had success stocking fingerling rainbow trout in CJ Strike in the past, capturing many of those fish years later as adults. This led to a willingness to try a batch of kokanee in the reservoir to see what level of success these fish can have in a new system.

Look for these kokanee to start showing up in the fishery as sub-adults as early as next spring and as adults in 2022.

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John Cassinelli