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Projected changes in Brook Trout and Brown Trout distribution in Wisconsin streams in the mid-twenty-first century in response to climate change

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Climate warming is a threat to the survival of fishes adapted to cold water. Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta are two cold-water species occurring in streams in Wisconsin, where climate change may make these species particularly vulnerable. Vulnerable trout populations need to be identified to aid in the development of adaptation strategies. We used web-based stream temperature and fish-distribution models in FishVis to predict current (late twentieth century) and project future (mid-twenty-first century) distributions of Brook Trout and Brown Trout. The models predict the suitability of habitat for trout in individual reaches using environmental variables in a geographic information system, including adjacent and upstream channel characteristics, surficial geology, landcover, and climate. Future projections of air temperature and precipitation were obtained from 13 general circulation models downscaled for Wisconsin. Currently, 34,251 km of streams are suitable for Brook Trout and 20,011 km for Brown Trout. The models project a decline of 68% (10,995 km) in stream habitat for Brook Trout and a decline of 32% (13,668 km) for Brown Trout. These projected declines, while substantial, were lower than earlier estimates because our models account for projected increased precipitation that may enhance groundwater inputs and partially offset higher air temperatures. (link to view paper online)
a Predicted Brook Trout occurrence (black) and absence (gray) for the current (late twentieth century) period; b Brook Trout vulnerability to habitat loss (percent of GCMs that project loss) for the future (mid-twenty-first century) period. Colors indicate the percent of GCMs that project Brook Trout loss: gray = already absent in the late twentieth century period, green = 0% (not vulnerable and likely to remain present), and light red = 1–20% (less vulnerable to loss) to dark red = 81–100% (more vulnerable to loss); c Brook Trout opportunity to gain habitat (percent of GCMs that project gain) for the future (mid-twenty-first century) period. Colors indicate the percent of GCMs that project Brook Trout gain: green = already present in the late twentieth century period, gray = 0% (no opportunity to gain and likely to remain absent), and light blue = 1–20% (less opportunity to gain) to dark blue = 81–100% (more opportunity to gain); d Brook Trout sensitivity to loss or gain of habitat (percent of GCMs that project loss or gain) for the future (mid-twenty-first century) period. Colors indicate the percent of GCMs that project Brook Trout loss or gain: green = present in the late twentieth century period and not likely to disappear, gray = absent in the late twentieth century period and not likely to reappear, and light purple = 1–20% (less sensitive to loss or gain) to dark purple = 81–100% (more sensitive to loss or gain)
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Projected changes in Brook Trout and Brown Trout
distribution in Wisconsin streams in the mid-twenty-first
century in response to climate change
Matthew G. Mitro .John D. Lyons .Jana S. Stewart .Paul K. Cunningham .
Joanna D. T. Griffin
Received: 20 July 2018 / Revised: 24 June 2019 / Accepted: 5 July 2019 / Published online: 29 July 2019
ÓThis is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2019
Abstract Climate warming is a threat to the survival
of fishes adapted to cold water. Brook Trout Salvelinus
fontinalis and Brown Trout Salmo trutta are two cold-
water species occurring in streams in Wisconsin,
where climate change may make these species partic-
ularly vulnerable. Vulnerable trout populations need
to be identified to aid in the development of adaptation
strategies. We used web-based stream temperature and
fish-distribution models in FishVis to predict current
(late twentieth century) and project future (mid-
twenty-first century) distributions of Brook Trout
and Brown Trout. The models predict the suitability of
habitat for trout in individual reaches using environ-
mental variables in a geographic information system,
including adjacent and upstream channel
characteristics, surficial geology, landcover, and cli-
mate. Future projections of air temperature and
precipitation were obtained from 13 general circula-
tion models downscaled for Wisconsin. Currently,
34,251 km of streams are suitable for Brook Trout and
20,011 km for Brown Trout. The models project a
decline of 68% (10,995 km) in stream habitat for
Brook Trout and a decline of 32% (13,668 km) for
Brown Trout. These projected declines, while sub-
stantial, were lower than earlier estimates because our
models account for projected increased precipitation
that may enhance groundwater inputs and partially
offset higher air temperatures.
Keywords Brook Trout Brown Trout Climate
change Fish distribution Wisconsin
Salmonids and other fishes adapted to cold water are
vulnerable to changes in thermal conditions that may
be attributable to climate warming. Streams that
support trout maintain relatively cold summer maxi-
mum water temperatures (Wehrly et al., 2007; Lyons
et al., 2010), so warming of stream temperatures from
climate change may threaten trout population persis-
tence (Lyons et al., 2010; Mitro et al., 2011; Roberts
et al., 2013). The state of Wisconsin in the north-
central United States has rich and varied cold-water
Guest editors: C. E. Adams, C. R. Bronte, M. J. Hansen,
R. Knudsen & M. Power / Charr Biology, Ecology and
M. G. Mitro (&)J. D. Lyons
Fisheries Research, Office of Applied Science, Wisconsin
Department of Natural Resources, 2801 Progress Road,
Madison, WI 53716, USA
J. S. Stewart
U.S. Geological Survey, 8505 Research Way, Middleton,
WI 53562, USA
P. K. Cunningham J. D. T. Griffin
Bureau of Fisheries Management, Wisconsin Department
of Natural Resources, 101 South Webster Street, Madison,
WI 53703, USA
Hydrobiologia (2019) 840:215–226,-volV)(0123456789().,-volV)
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Populations show little variation in their capacity to respond to temperature changes [47,48], though there is some evidence that populations from cooler climates have lower thermal tolerance [49]. Based on predicted climate scenarios, it is expected that suitable brook charr habitat will decrease over time across much of its native range [46,[50][51][52][53], including in Québec and eastern Canada, where suitable habitat would shift to the northeast [54], resulting in reduced growth and survival of individuals and ultimately persistence of populations [46,48,55]. Due to the thermal sensitivity and economic importance of the species, a thorough understanding of the mechanisms through which brook charr acclimate and cope with thermal stress is needed to refine predictions of climate change impacts on this species. ...
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... Our results contribute to a growing body of evidence that extreme seasonal weather associated with climate change will threaten population persistence of freshwater animals (Blum et al., 2018;Kanno et al., 2016;Lob on-Cervi a, 2004;Zorn & Nuhfer, 2007a) exacerbating the effects of direct habitat loss (Bell et al., 2021;Mitro et al., 2019;Wenger et al., 2011). We add to this body by demonstrating how the effects of seasonal air temperature and precipitation-which are both projected to increase under climate change in the Midwestern United States-can vary markedly by species, season, and location as populations responded differently in warm, southern regions compared with cool, northern regions. ...
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... For example, trout population inhabiting cold-transitional streams in Michigan declined in abundance when a mere 10% in flow reduction 1060 occurred because these streams had reference summer temperatures near the critical thermal tolerance levels for trout (Zorn et al., 2012). Similarly, stream temperatures in Wisconsin may reach critical maximum thresholds for stream trout mortality if both air temperature increases and baseflow declines Selbig, 2015), with Mitro et al. (2019) projecting a 68% 1065 and 32% decline in brook and brown trout thermal habitat by mid-century in response to warming summer air temperatures. ...
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... The modeling approach we implemented is flexible and could also be adapted to address other questions. For example, one could project the suitability of habitat for Brown Trout (or other species) under future climate scenarios if one had spatial data sets of predicted future values for variables of importance, like predicted July stream temperature (e.g., see Mitro et al. 2019). While machine learning models such as random forest may perform poorly when applied to new data outside of the bounds used in their training data sets (e.g., Wegner and Olden 2012), the Michigan Stream Status and Trends Program is well suited to avoid these limitations given that a wide range of stream types are currently sampled. ...
Evaluation of fisheries management actions are critical but can be challenging when management actions are applied at broad spatial scales. Likewise, evaluations can be limited if monitoring data are not available for comparison. One widely applied management strategy that can be difficult to evaluate at broad spatial scales is the stocking of fish. We used presence/absence data collected by 209 surveys of the Michigan Stream Status and Trends Program, a standardized statewide stream monitoring project, for Brown Trout Salmo trutta over 20.3 cm total length and landscape‐scale site predictor variables to generate a random forest model of Brown Trout presence or absence. The model had an overall error rate of 19% and was used to predict the presence and absence of Brown Trout in all Michigan stream segments (n = 68,123 stream segments). We evaluated model predictions using an independent data set containing 773 validation surveys. Validation surveys where Brown Trout were predicted present had catch rates 30% higher than validation surveys occurring at sites where Brown Trout were predicted absent, indicating biological relevance of model predictions. Comparisons with model predictions and recent Brown Trout stocking sites revealed that since 2002 Michigan has stocked nearly 9 million Brown Trout in streams our classification model predicted to be absent of Brown Trout over 20.3 cm, suggesting that field evaluation of those sites may be warranted to avoid ineffective use of resources. The model we developed can be used as a screening tool to identify the potential suitability of future stocking sites and prioritize existing stocking sites for field validation surveys to ensure efficient deployment of agency resources.
As climate change alters the thermal environment of the planet, interest has grown in how animals may mitigate the impact of a changing environment on physiological function. Thermal acclimation to a warm environment may, for instance, blunt the impact of a warming environment on metabolism by allowing a fish to shift to slower isoforms of functionally significant proteins such as myosin heavy chain. The thermal acclimation of brook trout (Salvelinus fontinalis) was examined by comparing swimming performance, myotomal muscle contraction kinetics and muscle histology in groups of fish acclimated to 4, 10 and 20 °C. Brook trout show a significant acclimation response in their maximum aerobic swimming performance (Ucrit), with acclimation to warm water leading to lower Ucrit values. Maximum muscle shortening velocity (Vmax) decreased significantly with warm acclimation for both red or slow-twitch and white or fast-twitch muscle. Immunohistochemical analysis of myotomal muscle suggests changes in myosin expression underly the thermal acclimation of swimming performance and contraction kinetics. Physiological and histological data suggest a robust acclimation response to a warming environment, one that would reduce the added metabolic costs incurred by an ectotherm when environmental temperature rises for sustained periods of time.
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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 prioritize 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.
Studies predicting how the distribution of aquatic organisms will shift with climate change often use projected increases in air temperature or water temperature. However, the assumed correlations between water temperature change and air temperature change can be problematic, especially for mountainous, high elevation streams. Using stream fish assemblage data from 1,442 surveys across a mountain - plains gradient (Wyoming, USA; 1990-2018), we compared the responsiveness of thermal guilds, native status groups, and assemblage structure to projected climate warming from generalized air temperature models and stream-specific water temperature models. Air temperature models consistently predicted greater range shift differences between warm-water and cold-water species, with air temperatures predicting greater increases in occurrence and greater range expansions for warm-water species. The "over-prediction" of warm-water species expansions resulted in air temperature models predicting higher rates of novel species combinations, greater increases in local species richness, and higher magnitudes of biotic homogenization compared with water temperature models. Despite differences in model predictions for warm-water species, both air and water temperature models predicted that three cold-water species would exhibit similar decreases in occurrence (decline of 1.0% and 1.8% of sites per 1 °C warming, respectively) and similar range contractions (16.6 and 21.5 m elevation loss per 1 °C warming, respectively). The "over-prediction" for warm-water species is partially attributable to water temperatures warming at slower rates than air temperatures because local, stream-scale factors (e.g., riparian cover, groundwater inputs) buffer high elevation streams from rising air temperatures. Our study provides the first comparison of how inferences about climate-induced biotic change at the species- and assemblage-levels differ when modeling with generalized air temperatures versus stream-specific water temperatures. We recommend future studies use stream-specific water temperature models, especially for mountainous, high elevation streams, to avoid the "over-prediction" of biotic changes observed from air temperature variables.
Technical Report
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Expected climatic changes in air temperature and precipitation patterns across the State of Wisconsin may alter future stream temperature and flow regimes. As a consequence of flow and temperature changes, the composition and distribution of fish species assemblages are expected to change. In an effort to gain a better understanding of how climatic changes may affect stream temperature, an approach was developed to predict and project daily summertime stream temperature under current and future climate conditions for 94,341 stream kilometers across Wisconsin. The approach uses a combination of static landscape characteristics and dynamic time-series climatic variables as input for an Artificial Neural Network (ANN) Model integrated with a Soil-Water-Balance (SWB) Model. Future climate scenarios are based on output from downscaled General Circulation Models (GCMs). The SWB model provided a means to estimate the temporal variability in groundwater recharge and provided a mechanism to evaluate the effect of changing air temperature and precipitation on groundwater recharge and soil moisture. The Integrated Soil-Water-Balance and Artificial Neural Network version 1 (SWB-ANNv1) Model was used to simulate daily summertime stream temperature under current (1990–2008) climate and explained 76 percent of the variation in the daily mean based on validation at 67 independent sites. Results were summarized as July mean water temperature, and individual stream segments were classified by thermal class (cold, cold transition, warm transition, and warm) for comparison of current (1990–2008) with future climate conditions. Integrating the SWB Model with the ANN Model provided a mechanism by which downscaled global or regional climate model results could be used to estimate the potential effects of climate change on future stream temperature on a daily time step. To address future climate scenarios, statistically downscaled air temperature and precipitation projections from 10 GCMs and 2 time periods were used with the SWB-ANNv1 Model to project future stream temperature. Projections of future stream temperatures at mid- (2046–65) and late- (2081–2100) 21st century showed the July mean water temperature increasing for all stream segments with about 80 percent of stream kilometers increasing by 1 to 2 degrees Celsius (°C) by mid-century and about 99 percent increasing by 1 to 3 °C by late-century. Projected changes in stream temperatures also affected changes in thermal classes with a loss in the total amount of cold-water, cold-transition, and warm-transition thermal habitat and a gain in warm-water and very warm thermal habitat for both mid- and late-21st century time periods. The greatest losses occurred for cold-water streams and the greatest gains for warm-water streams, with a contraction of cold-water streams in the Driftless Area of western and southern Wisconsin and an expansion of warm-water streams across northern Wisconsin. Results of this study suggest that such changes will affect the composition of fish assemblages, with a loss of suitable habitat for cold-water fishes and gain in suitable habitat for warm-water fishes. In the end, these projected changes in thermal habitat attributable to climate may result in a net loss of fisheries, because many warm-water species may be unable to colonize habitats formerly occupied by cold-water species because of other habitat limitations (e.g., stream size, gradient). Although projected stream temperatures may vary greatly, depending on the emissions scenario and models used, the results presented in this report represent one possibility. The relative change in stream temperature can provide useful information for planning for potential climate impacts to aquatic ecosystems. Model results can be used to help identify vulnerabilities of streams to climate change, guide stream surveys and thermal classifications, prioritize the allocation of scarce financial resources, identify approaches to climate adaptation to best protect and enhance resiliency in stream thermal habitat, and provide information to make quantitative assessments of statewide stream resources.
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Climate changes affect aquatic ecosystems by altering temperatures and precipitation patterns, and the rear edges of the distributions of cold-water species are especially sensitive to these effects. The main goal of this study was to predict in detail how changes in air temperature and precipitation will affect streamflow, the thermal habitat of a cold-water fish (the brown trout, Salmo trutta), and the synergistic relationships among these variables at the rear edge of the natural distribution of brown trout. Thirty-one sites in 14 mountain rivers and streams were studied in central Spain. Models of streamflow were built for several of these sites using M5 model trees, and a non-linear regression method was used to estimate stream temperatures. Nine global climate models simulations for Representative Concentration Pathways RCP4.5 and RCP8.5 scenarios were downscaled to the local level. Significant reductions in streamflow were predicted to occur in all of the basins (max. −49 %) by the year 2099, and seasonal differences were noted between the basins. The stream temperature models showed relationships between the model parameters, geology and hydrologic responses. Temperature was sensitive to streamflow in one set of streams, and summer reductions in streamflow contributed to additional stream temperature increases (max. 3.6 °C), although the sites that are most dependent on deep aquifers will likely resist warming to a greater degree. The predicted increases in water temperatures were as high as 4.0 °C. Temperature and streamflow changes will cause a shift in the rear edge of the distribution of this species. However, geology will affect the extent of this shift. Approaches like the one used herein have proven to be useful in planning the prevention and mitigation of the negative effects of climate change by differentiating areas based on the risk level and viability of fish populations.
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Brook trout habitat vulnerability was assessed within an Appalachian watershed. • Increased discharge largely offset effects of increased air temperature. • No consistent loss of suitable brook trout habitat by end of 21st century • However, periods of low flow resulted in a loss of habitat at the network-scale. • Persistence of refugia below tributaries should enable metapopulation persistence. We provide an assessment of thermal characteristics and climate change vulnerability for brook trout (Salvelinus fontinalis) habitats in the upper Shavers Fork sub-watershed, West Virginia. Spatial and temporal (2001–2015) variability in observed summer (6/1–8/31) stream temperatures was quantified in 23 (9 tributary, 14 main-stem) reaches. We developed a mixed effects model to predict site-specific mean daily stream temperature from air temperature and discharge and coupled this model with a hydrologic model to predict future (2016–2100) changes in stream temperature under low (RCP 4.5) and high (RCP 8.5) emissions scenarios. Observed mean daily stream temperature exceeded the 21 °C brook trout physiological threshold in all but one main-stem site, and 3 sites exceeded proposed thermal limits for either 63-and 7-day mean stream temperature. We modeled mean daily stream temperature with a high degree of certainty (R 2 = 0.93; RMSE = 0.76 °C). Predicted increases in mean daily stream temperature in main-stem and tributary reaches ranged from 0.2 °C (RCP 4.5) to 1.2 °C (RCP 8.5). Between 2091 and 2100, the average number of days with mean daily stream temperature N 21 °C increased within main-stem sites under the RCP 4.5 (0–1.2 days) and 8.5 (0 − 13) scenarios; however, no site is expected to exceed 63-or 7-day thermal limits. During the warmest 10 years, ≥ 5 main-stem sites exceeded the 63-or 7-day thermal tolerance limits under both climate emissions scenarios. Years with the greatest increases in stream temperature were characterized by low mean daily discharge. Main-stem reaches below major tributaries never exceed thermal limits, despite neighboring reaches having among the highest observed and predicted stream temperatures. Persistence of thermal refugia within upper Shavers Fork would enable persistence of metapopulation structure and life history processes. However, this will only be possible if projected increases in discharge are realized and offset expected increases in air temperature.
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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
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Significance Many studies predict climate change will cause widespread extinctions of flora and fauna in mountain environments because of temperature increases, enhanced environmental variability, and invasions by nonnative species. Cold-water organisms are thought to be at particularly high risk, but most predictions are based on small datasets and imprecise surrogates for water temperature trends. Using large stream temperature and biological databases, we show that thermal habitat in mountain streams is highly resistant to temperature increases and that many populations of cold-water species exist where they are well-buffered from climate change. As a result, there is hope that many native species dependent on cold water can persist this century and mountain landscapes will play an important role in that preservation.
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Despite increasing concern that climate change may negatively impact trout—a globally distributed group of fish with major economic, ecological, and cultural value—a synthetic assessment of empirical data quantifying relationships between climatic variation and trout ecology does not exist. We conducted a systematic review to describe how temporal variation in temperature and streamflow influences trout ecology in freshwater ecosystems. Few studies (n = 42) have quantified relationships between temperature or streamflow and trout demography, growth, or phenology, and nearly all estimates (96 %) were for Salvelinus fontinalis and Salmo trutta. Only seven studies used temporal data to quantify climate-driven changes in trout ecology. Results from these studies were beset with limitations that prohibited quantitatively rigorous meta-analysis, a concerning inadequacy given major investment in trout conservation and management worldwide. Nevertheless, consistent patterns emerged from our synthesis, particularly a positive effect of summer streamflow on trout demography and growth; 64 % of estimates were positive and significant across studies, age classes, species, and locations, highlighting that climate- induced changes in hydrology may have numerous consequences for trout. To a lesser degree, summer and fall temperatures were negatively related to population demography (51 and 53 % of estimates, respectively), but temperature was rarely related to growth. To address limitations and uncertainties, we recommend: (1) systematically improving data collection, description, and sharing; (2) appropriately integrating climate impacts with other intrinsic and extrinsic drivers over the entire lifecycle; (3) describing indirect consequences of climate change; and (4) acknowledging and describing intrinsic resiliency.
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The Driftless Area in southeastern Minnesota is on the southwestern edge of the native range of Brook Trout Salvelinus fontinalis. It was assumed that native Brook Trout were extirpated from this region in the early 1900s due to degraded stream conditions and stockings of eastern-origin Brook Trout and European Brown Trout Salmo trutta. Our objectives were to examine Brook Trout populations in the region to determine their spatial and genetic distribution and quantify population characteristics. Information on presence or absence of Brook Trout was gathered by electrofishing 174 streams in southeastern Minnesota. Brook Trout were present in 68% of coldwater streams compared with only in 3% in the early 1970s. The increase is likely due to increasing stream discharge throughout the Driftless Area, enabling recolonization or successful establishment of stocked populations. Streams with higher base flow discharge also had higher abundance, larger size at maturity, and larger Brook Trout present. Genetic data on 74 populations were analyzed to characterize genetic variation within populations, assess genetic structure among populations, and determine possible origins. Numerous populations were not associated with known hatchery sources but were primarily composed of geographic groupings that could represent remnant lineages. Although population characteristics were similar among genetic origins, potentially remnant populations should be given conservation priority because they have proven their ability to sustain themselves in this region. Management actions that emphasize maintaining or increasing stream base flows throughout the region will likely enhance remnant Brook Trout populations in the Driftless Area. Received July 25, 2014; accepted March 17, 2015
Responses of a wild brook trout (Salvelinus fontinalis) population to instream habitat development in a 0.7 km reach of Lawrence Creek were monitored for 7 years and compared to population data for the 3-year period prior to development. Mean annual biomass of trout, mean annual number of trout over 15 cm (legal size), and annual production increased significantly during the 3 years following development, but more impressive responses were observed during the second 3 years. Maximum number and biomass and number of legal trout did not occur until 5 years after completion of develop ment. The peak number of brook trout over 20 cm was reached the sixth year after develop ment. Where long-term studies of aquatic systems are needed to evaluate effects of environmental perturbations, it may be desirable to deliberately delay collection of posttreatment data. Such a start-pause-finish sequence of research would provide more valid and less costly evaluations and utilize the time of researchers more efficiently.
Riparian buffer strips can improve streams damaged by continuous livestock grazing, but they involve farmer costs that limit their application. We evaluated riparian intensive rotational grazing (IRG) as an alternative stream rehabilitation practice. We compared bank erosion, fish habitat characteristics, trout abundance, and a fish-based index of biotic integrity (IBI) among stations with either riparian continuous grazing, IRG, grassy buffers, or woody buffers along 23 trout stream reaches in southwestern Wisconsin during 1996 and 1997. After statistically factoring out watershed effects, stations with IRG or grassy buffers had the least bank erosion and fine substrate in the channel. Continuous grazing stations had significantly more erosion and, with woody buffers, more fine substrate. Station riparian land use had no significant effect on width/depth ratio, cover, percent pools, habitat quality index, trout abundance, or IBI score, but overall watershed conditions influenced these parameters. Buffers and IRG appear similarly effective for rehabilitating Wisconsin streams.