Kootenai River White Sturgeon: Parentage-based tagging

Parentage-based tagging (PBT) involves genotyping hatchery broodstock and using parentage assignment to identify exact parents of a hatchery origin fish of unknown parentage. This technique has been successfully utilized in other river spawning fishes but has yet to be validated and optimized for use in sturgeon. Previous research in other species indicates that the release of hatchery fish at earlier life stages improves overall survival and performance in the wild. However, young sturgeon cannot be released into the wild without a physical mark to identify hatchery origin versus wild origin fish. The requirement for physical marking necessitates keeping hatchery spawned fish in the hatchery for a year for them to reach sufficient size for physical marking. During this year in captivity, differential survival of fish selected for adaptation to the hatchery environment may ultimately result in lower survival rates once the fish are released into the river. PBT would solve this issue by allowing for genetic “tagging” of fish through genotyping of their parents so that they can be released as free embryos into the river. Juveniles caught in subsequent sampling can then be genetically assigned to their parents and identified as hatchery origin. If juveniles are caught that cannot be assigned to hatchery parents, we can then identify those individuals as wild origin fish.

We will use hatchery broodstock and juveniles from the Kootenai Tribe of Idaho as well as hatchery fish recaptured in the Kootenai River in 2020 (from the 2004-2019 year classes) and genotyped using SNPs to develop a PBT protocol. All individuals used in the development of PBT will be of known parentage to allow us to validate the accuracy of our methods. Our goal is to refine the PBT sampling and analysis pipeline such that we can assign sampled juveniles to their parents with a high degree (99%) of accuracy. If we are able to accomplish this, PBT will be implemented in the Kootenai River hatchery program, allowing for the release of free embryos from the hatchery into the river.

Anticipated Results: How will our work help WS conservation?

Current trends show extremely low recruitment of naturally spawned wild juveniles in the Kootenai River. Although there has been successful survival and growth in the wild of hatchery spawned and released juveniles, PBT will facilitate the release of free embryos rather than keeping fish in the hatchery for one year until physical marking is feasible. PBT will thus allow earlier release to help avoid the effects of domestication selection as well as evaluation of whether earlier release leads to a higher total number of juveniles surviving in the river. The earlier release will also result in substantial cost savings for hatcheries. These savings could facilitate the captive spawning of additional females each year, effectively increasing the genetic diversity of hatchery spawned and released fish. Lastly, PBT will help in the evaluation of a juvenile-rearing habitat restoration project slated for completion in 2020 on the Kootenai River. Previous releases of larval sturgeon in the early 2000s on the Kootenai River failed to produce surviving juveniles. PBT will allow for the release of larval fish onto the newly restored habitat, and if these fish are caught as juveniles in later sampling efforts, it will demonstrate the efficacy of this habitat restoration work.

Graduate Student Aviva Fiske.