Anadromy efficacy of native kokanee in Alturas Lake, Idaho

Abstract

Eaton KR, Tardy KA. 2022. Anadromy efficacy of native kokanee in Alturas Lake, Idaho. Lake Reserv Manage. XX:XX–XX. Partial migration is a complex process that can have profound impacts on ecosystems and populations. Oncorhynchus nerka ecotypes in the Sawtooth Valley include migratory and resident populations, with each exhibiting partial migration. Kokanee can exhibit anadromous behavior and therefore are valuable for O. nerka recovery. In the Sawtooth Valley, Alturas Lake supports a native kokanee population for which the ability to produce outmigrants could influence conservation decisions. In this study, we used contemporary genetic tools to identify the life history origin of Alturas Lake O. nerka outmigrants. Additionally we use population and survival estimates to determine the extent and success of any present kokanee migration. We found that in Alturas Lake, all juvenile outmigrants are progeny of native kokanee. We also found that increased population abundance is related to a higher number of outmigrants. Furthermore, juvenile survival estimates of Alturas kokanee outmigrants were similar to juvenile Redfish Lake sockeye salmon survival estimates. These similar survival estimates and return of anadromous kokanee adults throughout program history indicate that the Alturas Lake kokanee population is successful in exhibiting anadromous behavior. While kokanee are not a focus for O. nerka recovery, this study shows the importance of partial migration in a native kokanee population in preserving the anadromous life history strategy. Our results highlight that in locations with no sockeye salmon population, like Alturas Lake, native kokanee populations are vital to O. nerka recovery and should be monitored and protected accordingly. Supplemental data for this article is available online at https://doi.org/10.1080/10402381.2022.2026541.