Although Dworshak kokanee typically spawn at two years of age, they have been found to delay maturity until three when growth rates are slow. Given that two-year-old kokanee were the smallest on record in 2022, we predicted that many of those fish would delay maturity for another year, which would lead to high abundance of three-year-old kokanee in 2023. This is exactly what happened, as we observed a much higher abundance of three-year-olds in our annual surveys than ever before. These three-year-olds we similar in average length (~ 8.5 inches) to the two-year-olds. This makes sense biologically because it is typically the slowest growing fish that delay maturity until age three.

Based on last summer’s annual survey, we expect kokanee abundance in Dworshak will start to return to moderate levels. The extremely abundant year-classes that were produced in 2020-2021 are beginning to age out of the population. The 2022 year-class was closer to average production and as those fish reach two years of age in 2024 they will provide a moderate abundance of two-year-old kokanee. The decline in kokanee abundance should contribute to faster growth rates, and I expect anglers will start to encounter 10-11 inch kokanee by the peak summer fishing months in 2024. I’ve already received a few reports from winter fisherman catching good numbers of kokanee in the 9-9.5 inch range, and those fish should experience decent growth rates as the water warms.

Results from our 2023 annual survey also indicated low numbers of age-0 kokanee. We estimated the number of age-0 kokanee in the reservoir was only about 250,000, which is the lowest amount we’ve seen since 1996. This isn’t entirely unexpected – kokanee populations tend to boom and bust. When they are extremely abundant, they often have poor reproduction, probably because spawners are smaller which means they dig shallow, lower quality nests, and produce less and smaller eggs. The positive side of this low production is that it should lead to much faster growth rates, and we expect that by 2025 Dworshak will likely have 12-13 inch kokanee again.