Abstract
A robust monitoring network that provides quantitative information about the status of imperiled species at key life stages and geographic locations over time is fundamental for sustainable management of fisheries resources. For anadromous species, management actions in one geographic domain can substantially affect abundance of subsequent life stages that span broad geographic regions. Quantitative metrics (e.g., abundance, movement, survival, life history diversity, and condition) at multiple life stages are needed to inform how management actions (e.g., hatcheries, harvest, hydrology, and habitat restoration) influence salmon population dynamics. The existing monitoring network for endangered Sacramento River winter-run Chinook Salmon (SRWRC, Oncorhynchus tshawytscha) in California’s Central Valley was compared to conceptual models developed for each life stage and geographic region of the life cycle to identify relevant SRWRC metrics. We concluded that the current monitoring network was insufficient to diagnose when (life stage) and where (geographic domain) chronic or episodic reductions in SRWRC cohorts occur, precluding within- and among-year comparisons. The strongest quantitative data exist in the Upper Sacramento River, where abundance estimates are generated for adult spawners and emigrating juveniles. However, once SRWRC leave the upper river, our knowledge of their identity, abundance, and condition diminishes, despite the juvenile monitoring enterprise. We identified six system-wide recommended actions to strengthen the value of data generated from the existing monitoring network to assess resource management actions: (1) incorporate genetic run identification; (2) develop juvenile abundance estimates; (3) collect data for life history diversity metrics at multiple life stages; (4) expand and enhance real-time fish survival and movement monitoring; (5) collect fish condition data; and (6) provide timely public access to monitoring data in open data formats. To illustrate how updated technologies can enhance the existing monitoring to provide quantitative data on SRWRC, we provide examples of how each recommendation can address specific management issues
Highlights
IntroductionCalifornia’s Central Valley (the Central Valley) experiences extreme variation in precipitation compared to other regions in the United States (Dettinger et al 2011)
California’s Central Valley experiences extreme variation in precipitation compared to other regions in the United States (Dettinger et al 2011)
Several monitoring locations exist for juvenile SRWRC, only one provides a population abundance estimate: the Red Bluff Diversion Dam (RBDD) rotary screw trap (RST; Figure 1)
Summary
California’s Central Valley (the Central Valley) experiences extreme variation in precipitation compared to other regions in the United States (Dettinger et al 2011). The Central Valley supports the co-existence of four runs of Chinook Salmon (Oncorhynchus tshawytscha) that are adapted to exploit different ecological and physiological niches. Each has unique life history traits, such as the season they return to spawn, the duration of juvenile freshwater residence, and the timing and size of juvenile emigration (Yoshiyama et al 1998). This life history diversity results in adult salmon and juveniles occupying the Central Valley year-round. The timing of riverine and Delta water operations needed to protect salmon varies among the different runs (NMFS 2009). In most of the salmon monitoring network, it is unclear whether a juvenile salmon sampled at a location and point in time is from a stock that is listed as threatened or
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