Evaluating Water Temperature, Habitat and Fish Communities in Candidate Coolwater Streams in Illinois

Abstract

Coolwater streams are less common in Illinois than their warmwater counterparts, but because of their unique temperature patterns they have the potential to harbor biota not typically found in warmwater streams. However, these systems are poorly understood and few attempts to define and characterize coolwater streams have been made in Illinois. This study was designed to provide a comprehensive evaluation of coolwater streams as a foundation for managing these resources. The primary objectives of this study include validating initial attempts to locate cool streams, conducting in situ measurements of stream temperature throughout Illinois, characterizing physical components and biota in cool streams, and evaluating methods for rapid estimation of stream temperature. We were able to obtain 280 temperature records from 232 locations collected between 1999 and 2010 (early collections from previous studies). More than one third (35.3%) of sampled locations were classified as cold or cool (<21.0 oC mean daily July temperature). Although this proportion is artificially high since we targeted streams we suspected to be cool for monitoring in this study, one in five (20.8%) of our random survey of wadeable stream sites was observed to have coolwater conditions. In addition, maps of their distribution indicate that they are fairly common in some watersheds (e.g., Apple River, Rock River, upper Kishwaukee River). Prior to initiation of this study, potential coolwater streams were identified using the locations of fish species considered indicators of cool temperatures and a GIS derived model of potential groundwater discharge. Observed stream temperatures revealed that the majority of these fish species were not reliable as indicators of cool conditions and that the groundwater model was effective only under certain conditions. However, the distributions of four fish species (brook stickleback, longnose dace, mottled sculpin, brown trout) correlated well with cold and cool temperatures, and indicator analysis revealed a coldwater fish community type. Coolwater and warmwater fish communities were generally similar in their species makeup. Although it was beyond the scope of this study combining multiple characteristics into predictive models may hold promise for differentiating stream thermal patterns amongst Illinois streams. Landscape features, instream habitat, vegetation, fish, mussels, and macroinvertebrates were evaluated in streams where temperature data were available in an effort to discover characteristics that might aid in rapid estimation of thermal conditions. Few physical characteristics correlated well with stream temperature, and conclusive patterns related to prediction of thermal regime remain elusive. Vegetation character and macroinvertebrate taxa (including mussels) from summer collections were not related to coolwater conditions. Overall, few individual characteristics were related clearly to temperature. Models derived temperature classes were reviewed and revised for stream segments throughout Illinois as part of this study. Model predictions were more accurate in identifying the thermal character of stream segments than the biological indicators that were examined in this study. However, only a small fraction of all stream segments have been monitored for temperature and additional validation of the model is needed.Illinois Department of Natural Resourcesunpublishednot peer reviewe