Dilemma on the Kootenai River-The Risk of Extinction or When Does the Hatchery Become the Best Option
Vaughn L. Paragamian and Raymond C. P. Beamesderfer
Abstract.—In 1994, the Kootenai River white sturgeon Acipenser transmontanus was listed in the United States as an endangered species. Under provisions of the Endangered Species Act, a recovery plan was prepared and included two main recovery measures: (1) mitigation of spring flows for spawning and early life rearing, and (2) implementation of a conservation aquaculture and breeding plan to prevent extinction and sustain year-classes. The hatchery program was controversial and intended as a short-term measure as the flow mitigation strategy for wild fish developed. It called for the release each year of up to 1,000 white sturgeon from each of 10–12 families. It was believed that the mitigation of spring flows from Libby Dam would rapidly bring about recovery. However, after 8 years of flow mitigation and intensive monitoring and evaluation, it became apparent that recovery needs were more complex. Flow releases were not at the expected magnitude and habitat issues became a significant concern because the spawning location of sturgeon did not appear suitable (silt and sand) for adequate survival of eggs and larvae. Recruitment of wild fish was extremely low, while survival of hatchery sturgeon was higher than expected. Hatchery fish soon became abundant out numbering juvenile wild sturgeon by about 400:1. Assessment of sturgeon demographics, with extinction risk models, provided evidence that the wild population would be extinct within three decades and the population would be comprised almost exclusively of hatchery fish. Population projections described a significant near-term bottleneck in spawner numbers as the wild population diminished but hatchery fish had not yet matured. Managers are faced with a contentious dilemma of elevating the importance of the hatchery program by taking a higher proportion of the remaining wild spawners, escalating the number of hatchery releases, which could result in increasing the risk of inbreeding depression, loss of genetic diversity, genetic swamping, disease magnification, long term domestication, and intraspecific competition with wild recruits, compromising recovery. However, without significant hatchery intervention, the population could become a museum piece with no management options to benefit anglers. There will be disagreements, but risks must be considered, and we propose some compromises that may ease the intrusion of hatchery fish and provide management options.