We used temperature and fish data from streams across Michigan and Wisconsin to estimate upper thermal tolerance limits for brook trout Salvelinus fontinalis and brown trout Salmo trutta. Tolerance limits were estimated for the maximum daily mean temperature (MEANT), maximum daily maximum temperature (MAXT), and maximum daily temperature range (RNGT) at exposure lengths of 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, and 63 d. We found no difference in the upper thermal tolerance limit for brook and brown trout. For time periods of 1-14 d, the upper temperatures tolerated by trout decreased rapidly from 25.38C to 22.58C for MEANT and from 27.68C to 24.68C for MAXT. For time periods from 21 to 63 d, the upper temperatures tolerated by trout declined more gradually from 22.18C to 21.08C for MEANT and from 24.28C to 22.98C for MAXT. The 7-d upper tolerance limit was 23.38C for MEANT and 25.48C for MAXT. The maximum RNGT tolerated by trout varied as a function of mean temperature and length of exposure. Our findings suggest that chronic temperature effects as well as temperature fluctuation play an important role in limiting salmonid distributions and therefore should be considered when developing management objectives and water quality standards.

Summer air and stream water temperatures are expected to rise in the state of Wisconsin, U.S.A., over the next 50 years. To assess potential climate warming effects on stream fishes, predictive models were developed for 50 common fish species using classification-tree analysis of 69 environmental variables in a geographic information system. Model accuracy was 56·0-93·5% in validation tests. Models were applied to all 86 898 km of stream in the state under four different climate scenarios: current conditions, limited climate warming (summer air temperatures increase 1° C and water 0·8° C), moderate warming (air 3° C and water 2·4° C) and major warming (air 5° C and water 4° C). With climate warming, 23 fishes were predicted to decline in distribution (three to extirpation under the major warming scenario), 23 to increase and four to have no change. Overall, declining species lost substantially more stream length than increasing species gained. All three cold-water and 16 cool-water fishes and four of 31 warm-water fishes were predicted to decline, four warm-water fishes to remain the same and 23 warm-water fishes to increase in distribution. Species changes were predicted to be most dramatic in small streams in northern Wisconsin that currently have cold to cool summer water temperatures and are dominated by cold-water and cool-water fishes, and least in larger and warmer streams and rivers in southern Wisconsin that are currently dominated by warm-water fishes. Results of this study suggest that even small increases in summer air and water temperatures owing to climate warming will have major effects on the distribution of stream fishes in Wisconsin.

: Bioaccumulation of toxic environmental mercury may affect the vital rates of piscivores such as the common loon (Gavia immer). Although immediate effects of mercury on early development or reproduction can be determined from short‐term field studies or dosing experiments, long‐term effects on survival for a long‐lived species such as the common loon must be discerned from large, long‐term observational data sets. We analyzed band‐resight and mercury data for 776 adult loons in Wisconsin and New England, USA, from 1991 to 2001 to 1) estimate annual survival rates and 2) investigate the relation between mercury exposure and survival. The model‐averaged estimate of apparent survival was 0.87, whereas the approximate survival rate (accounting for movement) was 0.92. We found no differences in apparent survival by geographic location or sex and no relation between survival and mercury. Power analyses showed that we were only likely to detect differences in survival ≥3%. Small differences in survival (<3%), which may be important to loon population viability, were unlikely to be detected in our dataset. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):665–673; 2008)

We quantified seasonal abundances, apparent survival rates, movements, and habitat use of age‐0 rainbow trout Oncorhynchus mykiss in a 25‐km reach of the Henrys Fork of the Snake River, Idaho, to determine what factors limit recruitment to the population. Natural production of rainbow trout occurred in each year of the study (1995‐1997) and ranged from 158,000 to 306,000 age‐0 fish each summer. No significant loss of age‐0 rainbow trout occurred between summer and autumn; suitable habitat was present throughout the channel in all reaches and supported large abundances of age‐0 rainbow trout through this period. The greatest losses (77‐100%) occurred during winter and primarily involved fish from center‐channel macrophyte beds. Most river sections, which had only simple bank habitat, did not support any age‐0 rainbow trout through the entire winter. Overwinter survival was greatest (18‐23%) in Box Canyon, a river section characterized by complex bank habitat, high gradient, and large substrate. Fish that were marked in river sections with simple bank habitat in autumn had moved to sections with complex bank habitat by the following spring. Winter habitat limits rainbow trout recruitment in the Henrys Fork.

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We used recent developments in theoretical population ecology to construct basic models of common loon (Gavia immer) demography and population dynamics. We parameterized these models using existing survival estimates and data from long‐term monitoring of loon productivity and abundance. Our models include deterministic, 2‐stage, density‐independent matrix models, yielding population growth‐rate estimates (λ) of 0.99 and 1.01 for intensively studied populations in our Wisconsin, USA, and New Hampshire, USA, study areas, respectively. Perturbation analysis of these models indicated that estimated growth rate is extremely sensitive to adult survival, as expected for this long‐lived species. Also, we examined 20 years of count data for the 2 areas and evaluated support for a set of count‐based models of population growth. We detected no temporal trend in Wisconsin, which would be consistent with fluctuation around an average equilibrium state but could also result from data limitations. For New Hampshire, the model set included varying formulations of density dependence and partitioning of stochasticity that were enabled by the annual sampling resolution. The best model for New Hampshire included density regulation of population growth and, along with the demographic analyses for both areas, provided insight into the possible importance of breeding habitat availability and the abundance of nonbreeding adults. Based on these results, we recommend that conservation organizations include nonbreeder abundance in common loon monitoring efforts and that additional emphasis be placed on identifying and managing human influences on adult loon survival.

Decision-makers in inland fisheries management must balance ecologically and socially palatable objectives for ecosystem services within financial or physical constraints. Climate change has transformed the potential range of ecosystem services available. The Resist-Accept-Direct (RAD) framework offers a foundation for responding to climate-induced ecosystem modification; however, ecosystem trajectories and current practices must be understood to improve future decisions. Using Wisconsin's diverse inland fisheries as a case study, management strategies for recreational and subsistence fisheries in response to climate change were reviewed within the RAD framework. Current strategies largely focus on resist actions, while future strategies may need to shift toward accept or direct actions. A participatory adaptive management framework and co-production of policies between state and tribal agencies could prioritise lakes for appropriate management action, with the goal of providing a landscape of diverse fishing opportunities. This knowledge co-production represents a process of social learning requiring substantial investments of funding and time.

Changes in environmental conditions are expected to affect stream temperature and ultimately the presence of native Brook Trout Salvelinus fontinalis in Wisconsin streams. While change in climate may be an ultimate cause of Brook Trout loss, proximate causes may involve factors other than intolerance to high temperatures. Here I present data to support the hypothesis that species interactions among Brook Trout, naturalized Brown Trout Salmo trutta, and ectoparasitic copepods Salmincola edwardsii in the context of changing environmental conditions can lead to declines in Brook Trout recruitment and abundance. While S. edwardsii are endemic to Wisconsin streams and infect Brook Trout, they do not infect Brown Trout. Salmincola edwardsii were first documented in Ash Creek, Wisconsin, in 2010 and became epizootic in 2012. Conditions in 2012 conducive to an epizootic included anomalously warm stream temperatures, relative drought conditions, and an increasing sympatric population of Brown Trout. Infection prevalence increased from 42% in April 2012 to 95% in October. Average intensity of infection in 2012 was 5.5 copepods per age‐0 Brook Trout and 16.1 per Brook Trout age 1 and older. Variation in Brook Trout recruitment appeared to be related to stock size and environmental factors, including flood events, Brown Trout abundance, and S. edwardsii epizootics. In 2012, flow conditions were conducive to salmonid recruitment, but Brook Trout recruitment fell precipitously relative to that of Brown Trout. Recruitment of age‐0 Brook Trout during S. edwardsii epizootics in 2012–2014 decreased about 77% and 89% compared with recruitment in 2007–2011 and 2005–2006, respectively. Following three consecutive years of S. edwardsii epizootics and poor recruitment, Brook Trout were nearing extirpation from Ash Creek. The data support the hypothesis that species interactions among fish and an ectoparasitic copepod under stressful environmental and ultimately climatic conditions can be a proximate cause of native Brook Trout loss.Received February 15, 2016; accepted July 28, 2016 Published online September 30, 2016