Abstract
Two decades have passed since the initiation of the National Oceanic and Atmospheric Administration’s research program aimed at advancing the understanding of estuary and ocean ecology of U.S. West Coast Pacific salmon (Oncorhynchus spp.). In this review and prospectus, we summarize key findings from this program and describe a plan for transitioning it to better support Ecosystem-Based Management (EBM). While we focus on salmon research, our approach applies to research design generally. Our path forward involves increasing understanding of ecosystem processes to improve the dependability of scenario testing under novel conditions. Over the past two decades, we developed a conceptual model for how climate, predators, prey, fisheries, and human activities influence salmon. Knowledge gaps we identified from our conceptual model include limited understanding of salmon distributions, behavior, maturation dynamics, and population dynamics, and salmon interactions with predators, competitors, and prey during winter. We consider emerging risks and vulnerabilities facing salmon and propose analysis frameworks for evaluating them. Increased predator populations, coupled with climate change, pose increasing threats to West Coast salmon and will require new strategies and actions to mitigate their negative impacts. We propose research to support the development of decision-support tools to evaluate tradeoffs associated with alternative management strategies and to inform an adaptive ecosystem management system to improve the resilience of salmon populations and salmon-dependent fisheries.
Highlights
The 150-year decline of Pacific salmon (Oncorhynchus spp.) is well documented
Using the National Oceanic and Atmospheric Administration (NOAA) Fisheries West Coast salmon ecology program as our case study, we provide guidance on how, where, and what to consider in our discussion of risk assessment and knowledge gaps
Many currently used salmon forecasts along the Current Ecosystem (CCE) rely solely on observed salmon numbers at earlier stages in the lifecycle – i.e., using spawners, smolt outmigrants, or early returns of immature fish to predict the abundance of adults from the same cohort. This may limit the ability of environmental covariates, those measured at the critical time around ocean entry and applied to sibling-based forecasts, to increase the predictive power of these shortterm forecasts because they already incorporate effects of early environmental conditions on those cohorts
Summary
The 150-year decline of Pacific salmon (Oncorhynchus spp.) is well documented (see Nehlsen et al, 1991; Taylor, 1999). Develop objective-specific models for assessing the trade-offs between salmon and ecosystem components under varying managerial and environmental scenarios (e.g., increasing predators and upwelling dynamics). Incorporate salmon-centric model and processes into more inclusive ecosystem-level models (e.g., end-to-end) to evaluate the salmon-dependent trade-offs associated with variability in salmon at sea including human dimensions, predator dynamics, forage dynamics, and ecosystem resilience. Describing major ecosystem processes that affect salmon recruitment (i.e., resulting number of sub-adults), ecosystem component interactions with salmon recruitment, and integrating Tier 2 research findings into assessment and ecosystem-based management. Research strategies intended for simple, unidirectional aspects of salmon ocean ecology represent mechanistic relationships between ecosystem components and salmon recruitment These relationships are applicable to assessment and management of salmon populations (identified in green on inset diagram). Ecosystem processes that affect salmon recruitment (unidirectional objectives and products)
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