Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem

Abstract

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead ( Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook ( O . tshawytscha ) in the California Central Valley, coho ( O . kisutch ) in California and southern Oregon, sockeye ( O . nerka ) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids.

Can the creation of new freshwater habitat demographically offset losses of Pacific salmon from chronic anthropogenic mortality?

“…Salmon also need dynamic and diverse freshwater habitats to thrive, and compensation projects will be more effective if they consider natural evolutionary processes needed for the health and resilience of the species (Waples et al 2009;Beechie et al 2010;Booth et al 2016), especially considering the added challenges posed by accelerating climate change. For example, improving temperature and flow regimes through riparian restoration and increased food availability may improve the tolerance of salmon populations to warmer water temperatures induced by climate change (Crozier et al 2019). Our results support the conclusion that cumulative impacts from multiple sources of anthropogenic mortality on more than one life-stage can have compounding (i.e.…”

“…However, downstream reaches of streams and rivers are often less stable geomorphologically (Naiman et al 2000;Naiman et al 2008), and the substantial investment required to build compensation habitats in low-elevation floodplains could be lost if, or when, natural large flow events occur. Other challenges to building effective side-channels habitats include the need for connectivity between the compensation habitats and main channel, which is crucial to ensure the success of mitigation (Anderson et al 2014;Crozier et al 2019). For example, schooling of juveniles and limited migration may lower the carrying capacity of constructed side-channels by limiting the number of fry that move in from spawning or rearing grounds (Walters et al 2013).…”

“…Coho and other species of Pacific salmon (Oncorhynchus sp.) are ecologically, culturally, and economically important species in the PNW (Gende et al 2002;Naiman et al 2002), but have declined dramatically in recent decades (Slaney et al 1996;Gustafson et al 2007;Crozier et al 2019). The main causes of decline include poor marine survival, commercial and recreational harvest, climate change, competition from hatchery fish, and the degradation of freshwater habitats needed for spawning and rearing (Kareiva et al 2000;Chittenden et al 2010).…”

Energetic Status of Alaskan Chinook Salmon: Interpopulation Comparisons and Predictive Modeling Using Bioelectrical Impedance Analysis

“…The overall goals of this study were to quantify patterns in energetic status in populations of Alaskan Chinook Salmon and develop BIA models to provide fisheries managers and researchers with nonlethal tools for predicting the energetic status of this important species. Such methods may be particularly useful in light of the sensitive status of Chinook Salmon populations in Alaska and elsewhere (Crozier et al 2019). Our specific objectives were to (1) estimate and examine among-population differences in proximate composition (lipid, water, and protein content) for four populations of Alaskan Chinook Salmon; (2) build and evaluate predictive models based on the relationship between proximate components and BIA electrical measurements for the four populations; (3) assess the utility of using the models to predict energetic status among species by using Chinook Salmon and Chum Salmon Oncorhynchus keta BIA models; and (4) quantify the relationships among BIA-predicted energetic status, sex, and spawning location for a remote Chinook Salmon population in Southeast Alaska to evaluate the feasibility of using BIA in the field.…”

Unfamiliar Territory: Emerging Themes for Ecological Drought Research and Management

“…Disturbances like drought are proving to be one mechanism for the species range shifts and biome shifts expected with ongoing climate change. 114,145 The loss or replacement of valued ecosystem components such as pinyon pine, 146 wild salmon and trout, 147,148 or sage grouse 149 after drought represents a cultural or recreational loss to diverse groups of people. These losses and strong turnover in the ecological community also alters ecosystem processes in ways that affect goods and services people rely upon ( Figure 1C).…”