Climate Change, Ecosystem Impacts, and Management for Pacific Salmon

Abstract

As climate change intensifies, there is increasing interest in developing models that reduce uncertainties in projections of global climate and refine these projections to finer spatial scales. Forecasts of climate impacts on ecosystems are far more challenging and their uncertainties even larger because of a limited understanding of physical controls on biological systems. Management and conservation plans that explicitly account for changing climate are rare and even those generally rely on retrospective analyses rather than future scenarios of climatic conditions and associated responses of specific ecosystems. Using past biophysical relationships as a guide to predicting the impacts of future climate change assumes that the observed relationships will remain constant. However, this assumption involves a long chain of uncertainty about future greenhouse gas emissions, climate sensitivity to changes in greenhouse gases, and the ecological consequences of climate change. These uncertainties in forecasting biological responses to changing climate highlight the need for resource management and conservation policies that are robust to unknowns and responsive to change. We suggest how policy might develop despite substantial uncertainties about the future state of salmon ecosystems.

Centennial-scale fluctuations and regional complexity characterize Pacific salmon population dynamics over the past five centuries

“…However, management models that assume timeinvariant parameters (e.g., for carrying capacity or intrinsic productivity) are unrealistic representations of the biology in these systems, and a more realistic approach would allow for changes in the underlying model parameters through time (e.g., 37). As it is unlikely that we will ever gain a detailed enough mechanistic understanding of what drives variation in salmon production for every exploited stock to be able to anticipate abrupt changes, we would be wise to invest in management strategies that are robust to large, unpredictable shifts in productivity (38)(39)(40). Our results also suggest that future shifts in productivity are unlikely to be synchronous across all stocks, and a risk-averse approach to fisheries would allow fishers the flexibility to shift effort between watersheds and regions to integrate across spatial variability in salmon returns, as is currently the case in Bristol Bay (15,41).…”

Synchrony of Marine Fish Catches and Climate and Ocean Regime Shifts in the North Pacific Ocean

“…For instance, large-scale salmon enhancement projects have altered freshwater survival for salmon stocks and in doing so may have negatively affected wild salmon stocks and other species (Hilborn and Eggers 2001). Regime shifts FISH CATCH SYNCHRONY WITH CLIMATE REGIME SHIFTS may also mask problems that only become apparent in the future, so management strategies need to be robust and adaptive (Schindler et al 2008). Fishing has also affected the age structure in numerous fish populations and fisheries, with many of the older fish being removed from the population.…”

Bidirectional connectivity in rivers and implications for watershed stability and management

“…Building off the ideas outlined in this manuscript and previous insights from holistic perspectives on watershed science and management (Fausch et al 2002;Gomi et al 2002;Schindler et al 2008;Lertzman and Mackinnon 2014;McCluney et al 2014;Moore et al 2015), below I offer several observations regarding the nature of river systems. For each observation, I discuss a corresponding challenge for the policy and management of these systems and the opportunity to more effectively consider the connected nature of rivers.…”

“…Practices that facilitate resilience include protecting small populations, maintaining habitat, diversified fisheries, and managing for community resilience (Healey 2009). Indeed, policies that protect habitats and fish populations will preserve the existing portfolios of salmon biodiversity that enable stability and resilience (Ruckelshaus et al 2002;Schindler et al 2008Schindler et al , 2010Healey 2009;Moore et al 2010;Lapointe et al 2014;Anderson et al 2015). While there have been frameworks developed to achieve these goals (i.e., Wild Salmon Policy; Fisheries and Oceans Canada 2005), these frameworks arguably lack strong implementation or accountability.…”