2003: Perennial Stream, Intermittent Habitats: Impacts of a BMP on Fish

Saerom Park (Biology) Williams College

Fish communities in streams respond to both physical and biological factors that change along spatio-temporal axes. Paschal's Creek, a shallow, sandy, perennial creek located in the William and Mary College Woods, has an extremely unstable substrate; thus, examining physical factors may provide a better framework for understanding stream-fish communities in an environment greatly affected by stochastic events. Past studies have identified various physical features of habitats as significant in determining habitat preferences of stream fishes. The intent of this study was two-fold. First, we wanted a baseline set of quantitative data about fish in the perennial streams surrounding Lake Matoaka for future research. Second, better understanding of how species utilize the streams in our watersheds will contribute towards more responsible and meaningful stewardship of our local environment.

An initial survey of fish populations in Pascal's Creek during low-flow conditions yielded low numbers of fish, all cyprinids (Semotilus atromaculatus and Clinostomus funduloides). A survey conducted after a large storm event in the middle of July yielded very high numbers fish, including two additional species (Lepomis macrochirus and Gambusia holbrooki, a livebearer). Using regression analysis, we correlated seven physical characteristics with the number of fish collected at each habitat. Habitat length and width were the most significant variables in predicting the number of fish, together accounting for 62% of the variation in fish number per habitat. The source of the fish in the stream appears to be the detention basin BMP (Best Management Practice) at the headwaters of Paschal's Creek. The overflow of the BMP during the storm event swept fish downstream, where they were able to find deepwater habitats primarily created by sediment erosion around large, woody debris. Our results indicate that although Paschal's Creek may provide habitat for large populations of fish only intermittently - both along the length of the stream and over time - the stream and its well-buffered banks provide, nevertheless, vital refugia for species of fish that cannot survive aquatic conditions downstream in Lake Matoaka.

For additional documentation Saerom Park provided a PowerPoint Presentation entitled "Perennial Stream, Intermittent Habitats: Impacts of a BMP on Fish " provided here in PDF form.