Potential Consequences of Climate Change to Persistence of Cutthroat Trout Populations

Abstract

Warmer water, changes in stream flow, and the increasing frequency and intensity of other disturbances are among the factors associated with climate change that are likely to impact native trout populations in the western USA. We examined how three of these factors—increased summer temperatures, uncharacteristic winter flooding, and increased wildfires—are likely to affect broad‐scale population persistence among three subspecies of cutthroat trout Oncorhynchus clarkii. Our results suggest that as much as 73% of the habitat currently occupied by Bonneville cutthroat trout O. c. utah, 65% of that occupied by westslope cutthroat trout O. c. lewisi, and 29% of that occupied by Colorado River cutthroat trout O. c. pleuriticus will be at high risk from one or more of the these three factors. Within the next 50 years, wildfire, floods, and other disturbances may have a greater impact on population persistence than increasing water temperature alone. Our results also suggest that the risk will vary substantially within subspecies. For each subspecies, our analyses identified large portions of their ranges where all populations either currently fail to meet basic persistence criteria, are at high risk from climate change, or both, indicating a high likelihood of losing the genetic and life history diversity in those areas. Stress from climate change is likely to compound existing problems associated with habitat degradation and introgression from introduced salmonids. Recognition of the increased risk from climate change may warrant altering the management paradigm of isolation and require increased control efforts for invasive nonnative species. Regardless of the management avenue chosen, more populations are likely to become isolated and vulnerable in the near future. Our results argue for immediate restoration actions within certain subbasins to increase the resistance and resilience of at‐risk populations and habitats to additional disturbances caused by rapid climate change.

Stock discrimination of two insular populations of Diplodus annularis (Actinopterygii: Perciformes: Sparidae) along the coast of Tunisia by analysis of otolith shape

“…These authors emphasized the existence of two genetically different populations for each species, a coastal population with a small size and a pelagic population with a larger size. Differences in hydrological regime between regions are generally reported as a barrier to delineate populations (Williams et al 2009). …”

A Fine-scale Assessment of Using Barriers to Conserve Native Stream Salmonids: A Case Study in Akokala Creek, Glacier National Park, USA

“…Such an approach allows competing considerations, such as accessibility for construction, to be weighed against biological considerations. Furthermore, because climate change is likely to exacerbate existing problems of habitat degradation and introduced salmonids, understanding the increased risk from climate change is needed to inform isolation management opportunities and may require increased control efforts for invasive nonnative species [7]. We recommend a two-stage approach of broad scale and high resolution assessments that will enable managers to comprehensively understand the complexities of using barriers and reliably evaluate the potential impacts on native salmonid species from local population to metapopulation scales.…”

“…Second, we used the mean catch estimate plus one standard deviation of the mean (less conservative), resulting in about a two-fold increase (mean = 1.8) of the mean single-pass catch, which is generally the proportion of westlope cutthroat trout captured on the first pass using multiple depletion population techniques in the Flathead system [34]. Lastly, we used the high cutthroat trout abundance estimate of 0.3 fish/m as reported by Hilderbrand and Kershner (2000), which equals or exceeds most interior cutthroat trout abundances [7,8], representing an optimistic scenario for estimating N e . We assumed that there were no population losses (i.e., mortality or dispersal) in each of these approaches.…”

Conserving Peripheral Trout Populations: The Values and Risks of Life on the Edge

“…Of course, the results of broad-scale assessments, including ours, should be augmented with finer-scale stream and population data to inform management decisions, but our results may be useful in identifying those populations that are in greatest need of management attention. For example, peripheral populations that fall far below persistence thresholds and/or are in high-risk areas for climate change-driven disturbance (Rieman et al 2007;Williams et al 2009) should receive initial attention. Declines of remaining peripheral populations are not likely to be consistent across all river basins or geographic areas.…”