Nez Perce Tribe White Sturgeon Management Plan in The Snake River Between Lower Granite and Hells Canyon Dams

摘要

White sturgeon in the Hells Canyon reach (HCR) of the Snake River are of cultural importance to the Nez Perce Tribe. However, subsistence and ceremonial fishing opportunities have been severely limited as a result of low numbers of white sturgeon in the HCR. Hydrosystem development in the Columbia River Basin has depressed numbers and productivity of white sturgeon in the HCR by isolating fish in impounded reaches of the basin, restricting access to optimal rearing habitats, reducing the anadromous forage base, and modifying early life-history habitats. Consequently, a proactive management plan is needed to mitigate for the loss of white sturgeon production in the HCR, and to identify and implement feasible measures that will restore and rebuild the white sturgeon population to a level that sustains viability and can support an annual harvest. This comprehensive and adaptive management plan describes the goals, objectives, strategies, actions, and expected evaluative timeframes for restoring the white sturgeon population in the HCR. The goal of this plan, which is to maintain a viable, persistent population that can support a sustainable fishery, is supported by the following objectives: (1) a natural, stable age structure comprising both juveniles and a broad spectrum of spawning age-classes; (2) stable or increasing numbers of both juveniles and adults; (3) consistent levels of average recruitment to ensure future contribution to reproductive potential; (4) stable genetic diversity comparable to current levels; (5) a minimum level of abundance of 2,500 adults to minimize extinction risk; and (6) provision of an annual sustainable harvest of 5 kg/ha. To achieve management objectives, potential mitigative actions were developed by a Biological Risk Assessment Team (BRAT). Identified strategies and actions included enhancing growth and survival rates by restoring anadromous fish runs and increasing passage opportunities for white sturgeon, reducing mortality rates of early life stages by modifying flows in the HCR, reducing mortality imposed by the catch and release fishery, augmenting natural production through translocation or hatchery releases, and assessing detrimental effects of contaminants on reproductive potential. These proposed actions were evaluated by assessing their relative potential to affect population growth rate and by determining the feasibility of their execution, including a realistic timeframe (short-term, mid-term, long-term) for their implementation and evaluation. A multi-pronged approach for management was decided upon whereby various actions will be implemented and evaluated under different timeframes. Priority management actions include: Action I- Produce juvenile white sturgeon in a hatchery and release into the management area; Action G- Collect juvenile white sturgeon from other populations in the Snake or Columbia rivers and release them into the management area; and Action D- Restore white sturgeon passage upriver and downriver at Lower Snake and Idaho Power dams. An integral part of this approach is the continual monitoring of performance measures to assess the progressive response of the population to implemented actions, to evaluate the actions efficacy toward achieving objectives, and to refine and redirect strategies if warranted.