You are here:
LANDSCAPE CHARACTER AND FISH ASSEMBLAGE STRUCTURE AND FUNCTION IN WESTERN LAKE SUPERIOR STREAMS: GENERAL RELATIONSHIPS AND IDENTIFICATION OF THRESHOLDS
Citation:
Brazner, J. C., D K. Tanner, N E. Detenbeck, S L. Batterman, S. L. Stark, L. A. Jagger, AND V M. Snarski. LANDSCAPE CHARACTER AND FISH ASSEMBLAGE STRUCTURE AND FUNCTION IN WESTERN LAKE SUPERIOR STREAMS: GENERAL RELATIONSHIPS AND IDENTIFICATION OF THRESHOLDS. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 33(6):855-875, (2004).
Impact/Purpose:
to determine the influence of hydrogeomorphic region, forest fragmentation, and watershed storage on fish assemblage structure and function
Description:
As part of a comparative watershed project investigating land cover/land use disturbance gradients for streams in the western Lake Suerior Basin, we wanted to determine the influence of hydrogeomorphic region, forest fragmentation, and watershed storage on fish assemblage structure and function. Geographic analysis of 362 second and 90 third order watersheds for mature forest cover, and total wetland/lake area allowed us to select 48 second and third order watersheds from two hydrogeomorphic regions to examine fish assemblage response to landscape treatment factors. During the summers of 1997 and 1998, electrofishing gear was used to sample fish from stream reaches along fragmentation and watershed storage gradients in each region. Each of the landscape factors significantly influenced fish assemblage structure and function. Watershed storage influenced the greatest number of fish assemblage characteristics, but hydrogeomorphic region and forest fragmentation played important roles, with region mediating effects of both watershed storage and fragmentation. Response thresholds identified by marked shifts in fish assemblage structure or function averaged 11% for watershed storage and 50% for watershed mature forest cover based on piecewise regression analysis. Our results suggest that regional differences in hydrogeomorphology and watershed-specific conditions interact in a highly interdependent manner to influence the structure and function of stream fish assemblages in western Lake Superior streams. Although many of the landscape influences we observed may have been mandated through effects on in-stream habitat, our results highlight the importance of management and land-use planning decisions at the watershed scale.