Field‐Based Estimates of Thermal Tolerance Limits for Trout: Incorporating Exposure Time and Temperature Fluctuation

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 25.3°C to 22.5°C for MEANT and from 27.6°C to 24.6°C for MAXT. For time periods from 21 to 63 d, the upper temperatures tolerated by trout declined more gradually from 22.1°C to 21.0°C for MEANT and from 24.2°C to 22.9°C for MAXT. The 7‐d upper tolerance limit was 23.3°C for MEANT and 25.4°C 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.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141436/1/tafs0365.pd

A Comparison of Statistical Approaches for Predicting Stream Temperatures Across Heterogeneous Landscapes 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73725/1/j.1752-1688.2009.00341.x.pd

Classifying Regional Variation in Thermal Regime Based on Stream Fish Community Patterns

Although the importance of water temperature to the ecology of stream fishes is well documented, relatively little information is available on the extent of regional variation in thermal regime and its influence on stream fish distribution and abundance patterns. In streams draining the heterogeneous glacial landscape of Michigan’s Lower Peninsula, regional variation in summer mean temperature and temperature fluctuation is among the highest reported in the literature. We developed a habitat classification to simplify the description of thermal regimes and to describe the relationships between available thermal regimes and distribution patterns of stream fishes. Changes in community composition, species richness, and standing stocks of key fish species occurred across gradients in mean temperature and temperature fluctuation. These changes were used to identify three mean temperature categories (cold, <19°C; cool, 19–<22°C; and warm, ≥22°C) and three temperature fluctuation categories (stable, <5°C; moderate, 5–<10°C; and extreme, ≥10°C). The combination of these categories resulted in a 3 × 3 matrix with nine discrete thermal regimes. The classification developed in this study provides a framework for descriptions of the realized thermal niche of stream fishes, and can be used as a baseline for measurement of changes in distribution patterns associated with future climate warming. Our results suggest that observed differences in community structure among sites are largely attributable to spatial variation in mean temperature and temperature fluctuation. Thus, accounting for the linkage between regional variation in thermal regime and fish community structure should improve our ability to effectively assess and manage stream resources.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141912/1/tafs0018.pd

A Landscapeâ Based Classification of Fish Assemblages in Sampled and Unsampled Lakes

We related fish species patterns and landscapeâ scale environmental data from 216 Michigan lakes to identify repeatable types of fish assemblages, identify environmental factors related to assemblage types, and classify fish assemblages in unsampled lakes. Multivariate regression tree modeling of fish species abundances identified six assemblage types that were explained by degreeâ days during the iceâ free period, lake surface area, and mean lake surface temperature. Warmwater species dominated southern lakes, while coolwater and coldwater species had higher abundances in northern lakes. Coolwater species were present in large southern lakes, whereas warmwater species were excluded from northern lakes that had low mean surface temperatures or low degreeâ days. These results suggest that patterns of lake fish assemblages are shaped by differences in climate as well as lakeâ specific differences in surface temperature regimes and in vertical availability of coldwater and coolwater habitats. Because we related fish patterns to readily available landscapeâ level data, our approach can be used to characterize fish assemblages in all lakes across broad geographic extents.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142256/1/tafs0414.pd

The Great Lakes Hydrography Dataset: Consistent, Binational Watersheds for the Laurentian Great Lakes Basin

Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km2, or about twice the 247,003 km2 surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134077/1/jawr12435_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134077/2/jawr12435.pd

The effect of temperature on the growth of juvenile lake sturgeon, Acipenser fulvescens

Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/115684/1/39015038121433.pd

The Effect of Temperature on the Growth of Juvenile Lake Sturgeon, Acipenser fulvescens. (Fisheries research report: 2004)

Master of ScienceNatural Resources and EnvironmentUniversity of Michigan, School of Natural Resources and Environmenthttp://deepblue.lib.umich.edu/bitstream/2027.42/40232/1/aag2862.2004.001.pd

Developing a resist-accept-direct (RAD) framework for managing freshwater fish species shifting in and out of political jurisdictions

Factors including human dispersal, climate change and varied environmental stressors are altering fish species distributions. Range expansions are producing new records of freshwater species which were rare or previously absent from regional jurisdictions (states, provinces and territories). Simultaneously, species are facing declines and local extirpations in some areas of their distribution. The Resist-Accept-Direct (RAD) framework can provide guiding principles for how declining, newly arrived, or range expanding freshwater fishes should be managed and how range-wide trends can be considered in local management and conservation decisions. We examine the principles of the framework and provide an example decision tree which is applied to examples ranging from resisting the establishment of potentially harmful non-native fishes, to accepting and providing refuge to those species threatened in other parts of their ranges, to directing the migration of fishes which improve ecosystem services. Applying this framework may improve coordination between agencies aiming to improve the resilience of freshwater ecosystems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/173080/1/fme12546_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/173080/2/fme12546.pd

Decision support for aquatic restoration based on species-specific responses to disturbance

Disturbances to aquatic habitats are not uniformly distributed within the Great Lakes and acute effects can be strongest in nearshore areas where both landscape and within lake effects can have strong influence. Furthermore, different fish species respond to disturbances in different ways. A means to identify and evaluate locations and extent of disturbances that affect fish is needed throughout the Great Lakes. We used partial Canonical Correspondence Analysis to separate “natural” effects on nearshore assemblages from disturbance effects. Species-specific quadratic models of fish abundance as functions of in-lake disturbance or watershed-derived disturbance were developed separately for each of 35 species and lakewide predictions mapped for Lake Erie. Most responses were unimodal and more species decreased in abundance with increasing watershed disturbance than increased. However, eight species increased in abundance with current in-lake disturbance conditions. Optimum Yellow Perch (Perca flavescens) abundance occurred at in-lake disturbance values less than the gradient mean, but decreased continuously from minimum watershed disturbance to higher values. Bands of optimum in-lake conditions occurred throughout the eastern and western portions of the Lake Erie nearshore zone; some areas were less disturbed than desirable. However, watershed-derived disturbance conditions were generally poor for Yellow Perch throughout the lake. In contrast, optimum Smallmouth Bass (Micropterus dolomieu) abundance occurred at in-lake disturbance values greater than the gradient mean and continuously increased with increasing watershed disturbance. Smallmouth Bass responses to disturbance indicated that most of the nearshore zone was less disturbed than is desirable and were most abundant in areas that the Yellow Perch response indicated were highly disturbed. Mapping counts of species response models that agreed on the disturbance level in each spatial unit of the nearshore zone showed a fine-scale mosaic of areas in which habitat restoration may benefit many or few species. This tool may assist managers in prioritizing conservation and restoration efforts and evaluating environmental conditions that may be improved.Species-specific non-linear responses of abundance to Great Lakes disturbance indices for multiple fish species identifies multiscale distributions of disturbed habitat perceived by each species throughout the lakes. The degree of agreement among species was mapped. The results provide decision support for population and community conservation and restoration efforts.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/191645/1/ece39313_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/191645/2/ece39313.pd

Influence of Spatial Extent on Contemporary and Future Threat Evaluation for Imperiled Fluvial Fishes and Mussels

Species conservation often faces many challenges, such as addressing threats from multiple stressor sources, representing under-studied taxa, and understanding implications of spatial extent. To overcome these challenges, we assessed contemporary anthropogenic threats from stream fragmentation and landscape disturbance as well as future habitat suitability under climate change for traditionally well-studied (fishes) and under-studied (mussels) imperiled fluvial taxa in Michigan, USA. To understand how threats to species vary spatially, predicted habitat suitability was analyzed for three hierarchically nested spatial extents: statewide, within species&rsquo; biogeographic ranges, and within river patches fragmented by barriers. Comparison of current and future habitat suitability for 27 fish and 23 mussel species indicates large potential statewide gains for many warmwater and/or large river fishes and several mussel species, however these gains are greatly diminished by biogeographic range limitations and habitat fragmentation among current and future habitats. One mussel species and several cold- and coolwater fishes are projected to have significant habitat losses under climate change irrespective of spatial extent. On average, 79% of habitats for mussels and 58% for fishes were considered moderately to severely disturbed from current human landscape activities. Habitat fragmentation was greater for fishes than mussels, with large dams playing a primary role in fragmenting habitats relative to small dams and waterfalls. Results indicate that threat assessments can vary substantially according to spatial extent and taxa, and consideration of both contemporary and future threats to habitats is needed to inform conservation of imperiled fluvial organisms