Monitoring and Research is Needed to Manage the Recovery of Threatened and Endangered Chinook and Steelhead in the Sacramento-San Joaquin Basin

摘要

In this report, we assess whether existing monitoring activities in the Central Valley are sufficient to determine if biological recovery goals are being met, and make recommendations for monitoring and research that could provide critically-needed information for effective management of Chinook salmon and steelhead beyond simple viability assessments. Assessing population status requires, at a minimum, estimates of abundance on the spawning grounds and the fraction of naturally-spawning fish that are of hatchery origin. We find that such data are generally available for independent populations of Chinook salmon, but are almost entirely unavailable for steelhead populations. Effective monitoring of steelhead run sizes at the population scale is needed urgently. Effective management of listed salmonids requires more information than simply whether populations and ESUs are achieving viability targets. We anticipate that managers will need information on the response of salmonid populations to regional climate change, the use of freshwater habitat, mechanisms and magnitude of mortality in freshwater and the ocean, age- and stock-specific harvest rates, trends in effective population size and genetic diversity within and among populations, the effects of hatchery operations on naturally spawning populations, how to go about reintroducing fish to reconnected or restored habitats, and the factors controlling and the implications of variable life history tactics of steelhead. We discuss why these information gaps need to be filled, and offer some suggestions on promising approaches to filling them. Finally, we recommend that new and existing data should be made accessible to researchers and managers through a central data portal that can aggregate information from the many existing databases.