Thermal controls of Yellowstone cutthroat trout and invasive fishes under climate change

We combine large observed data sets and dynamically downscaled climate data to explore historic and future (2050-2069) stream temperature changes over the topographically diverse Greater Yellowstone Ecosystem (elevation range=824-4017m). We link future stream temperatures with fish growth models to investigate how changing thermal regimes could influence the future distribution and persistence of native Yellowstone cutthroat trout (YCT) and competing invasive species. We find that stream temperatures during the recent decade (2000-2009) surpass the anomalously warm period of the 1930s. Climate simulations indicate air temperatures will warm by 1 °C to >3 °C over the Greater Yellowstone by mid-21st century, resulting in concomitant increases in 2050-2069 peak stream temperatures and protracted periods of warming from May to September (MJJAS). Projected changes in thermal regimes during the MJJAS growing season modify the trajectories of daily growth rates at all elevations with pronounced growth during early and late summer. For high-elevation populations, we find considerable increases in fish body mass attributable both to warming of cold-water temperatures and to extended growing seasons. During peak July to August warming, mid-21st century temperatures will cause periods of increased thermal stress, rendering some low-elevation streams less suitable for YCT. The majority (80%) of sites currently inhabited by YCT, however, display minimal loss (<10%) or positive changes in total body mass by midcentury; we attribute this response to the fact that many low-elevation populations of YCT have already been extirpated by historical changes in land use and invasions of non-native species. Our results further suggest that benefits to YCT populations due to warmer stream temperatures at currently cold sites could be offset by the interspecific effects of corresponding growth of sympatric, non-native species, underscoring the importance of developing climate adaptation strategies that reduce limiting factors such as non-native species and habitat degradation.Keywords: trout, climate change, growth, non-natives, Greater Yellowston

Management Effectiveness of the World's Marine Fisheries

A global analysis shows that fishery management worldwide is lagging far behind international standards, and that the conversion of scientific advice into policy, through a participatory and transparent process, holds promise for achieving sustainable fisheries

Detecting Declines in the Abundance of a Bull Trout (Salvelinus confluentus) Population: Understanding the Accuracy, Precision, and Costs of Our Efforts

Using empirical field data for bull trout (Salvelinus confluentus), we evaluated the trade-off between power and sampling effort–cost using Monte Carlo simulations of commonly collected mark–recapture–resight and count data, and we estimated the power to detect changes in abundance across different time intervals. We also evaluated the effects of monitoring different components of a population and stratification methods on the precision of each method. Our results illustrate substantial variability in the relative precision, cost, and information gained from each approach. While grouping estimates by age or stage class substantially increased the precision of estimates, spatial stratification of sampling units resulted in limited increases in precision. Although mark–resight methods allowed for estimates of abundance versus indices of abundance, our results suggest snorkel surveys may be a more affordable monitoring approach across large spatial scales. Detecting a 25% decline in abundance after 5 years was not possible, regardless of technique (power = 0.80), without high sampling effort (48% of study site). Detecting a 25% decline was possible after 15 years, but still required high sampling efforts. Our results suggest detecting moderate changes in abundance of freshwater salmonids requires considerable resource and temporal commitments and highlight the difficulties of using abundance measures for monitoring bull trout populations

Surveying professional opinion to inform bull trout recovery and management decisions

Increasing concerns about management and recovery of the threatened bull trout (Salvelinus confluentus) prompted the Bull Trout Committee of Western Division American Fisheries Society to survey scientists working most closely with bull trout in Pacific Northwest drainages of the contiguous United States. We solicited scientific and judgment-based assessments regarding current status and future trends, limiting factors, effectiveness of restoration strategies and regulatory mechanisms, and information gaps. The survey was sent to 235 biologists, with the majority of the responses coming from Montana, Oregon, and Washington. Respondents indicated fish passage, forest management practices, and normative species interactions are the primary factors limiting bull trout populations, and these issues were identified as the primary recovery challenges in the foreseeable future. Survey results indicated large information gaps in our understanding of bull trout population dynamics, monitoring and evaluation, and community interactions. Finally, survey respondents across demographic groups identified the listing under the Endangered Species Act as the single most important regulatory action benefiting bull trout. We conclude online surveys of professional opinions can be useful for guiding future management decisions, identifying research needs, understanding the relative importance of potential limiting factors, and evaluating the effectiveness of different regulatory mechanism