Factors Affecting Allopatric and Sympatric Occurrence of Two Sculpin Species across a Rocky Mountain Watershed
We assessed factors related to the occurrence of allopatric and sympatric Paiute Sculpin (Cottus beldingi) and Mottled Sculpin (Cottus bairdi) in the Salt River watershed of Wyoming and Idaho, 1996–1997. Sympatric occurrences of Paiute Sculpin and Mottled Sculpin were found in downstream segments of tributaries across a wide range of elevations, stream temperatures, channel slopes, and stream sizes. Allopatric Paiute Sculpin was found in small, high-elevation streams with low summer water temperatures, high channel slopes, large rocky substrates, and low densities of Brown Trout (Salmo trutta). Allopatric Mottled Sculpin occurred in spring streams that were wide and deep, dominated by fine substrate, and supported high densities of Brown Trout. Mottled Sculpin was absent from all tributaries on the eastern side of the drainage where streams have low summer water temperatures, high-gradient channels, and barriers that can influence upstream movements. This study suggests that stream geomorphology, thermal characteristics, local habitat conditions, and nonnative fishes differentially influence the occurrence of Paiute Sculpin and Mottled Sculpin.Abstract
Map showing the locations of reaches sampled and distributions of allopatric and sympatric Paiute Sculpin (PSC) and Mottled Sculpin (MSC) in the Salt River watershed of Wyoming and Idaho, 1996– 1997. Open symbols represent sampling reaches and dark bars represent large (> 1 m high), permanent barriers to upstream movement by fishes. Stream segments represented as dotted lines indicate that reaches are frequently intermittent or dewatered
Canonical discriminant analysis used to identify factors related to the occurrence of allopatric and sympatric Paiute Sculpin (PSC) and Mottled Sculpin (MSC) in the Salt River watershed of Wyoming and Idaho, 1996–1997. The first canonical axis (CAN1) was primarily comprised of mean wetted width (m), the proportion of fine substrate (%), the abundance of Brown Trout (number/100 m), and elevation (meters above mean sea level). The second canonical axis (CAN2) was primarily comprised of mean summer water temperature (July and August, C)
Contributor Notes
U.S. Geological Survey–Biological Resources Division, Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Laramie, Wyoming 82071–3166. Present address: (DJI) University of Idaho, Ecohydraulics Research Group, Department of Civil Engineering, Boise, Idaho 83712. (MCQ) mcquist@uwyo.edu Send reprint requests to MCQ.