The importance of ecoregion versus drainage area on fish distributions in the St. Croix River and its Wisconsin tributaries

• Published in: Environmental biology of fishes Vol. 55; no. 3; pp. 245 - 254
• Main Authors: NEWALL, P. R, MAGNUSON, J. J
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01-07-1999; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biota; Classification; Creeks & streams; Drainage; Drainage area; Ecosystem structure; Ecosystems; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; North America, St. Croix R; Pisces; Resource management; River basins; Rivers; Synecology; USA, Wisconsin; USA, Wisconsin, St. Croix R; United States; North America; Wisconsin; America; USA, Wisconsin, St. Croix R; Site; Community structure; Gradient; Landscape; Drainage basins; Size; Freshwater environment; Vertebrata; Geographic distribution; Animal community; Pisces; Classification; Stream
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1023/A:1007527800434

Aquatic ecoregions, based on regional landscape features, have been proposed as a model for aquatic resource management. The model assumes the existence of a typical biota associated with a given ecoregion and serves as the basis for biological assessment, reference site designation, and determination of stream potential, based on this biotic assemblage. Contrasting models for predicting stream ecosystem structure focus on the importance of local site conditions, including the regular and predictable changes that occur as a function of area draining to a site. In this study, a classification of 429 stream sites over an area of approximately 20000km^sup 2^ in the St. Croix River basin delineated three major species groups: redhorse/spotfin shiner; brook charr/sculpin; and mixed species. Numerical analyses revealed no relationship between the species communities and ecoregions. In contrast, there was a strong association between the species communities and the area draining to the site. Our study highlights the importance of accommodating the inherent structure associated with site drainage area when imposing a regionally-based ecological classification upon stream ecosystems. This structure is expressed in the systematic changes to the physical habitat that occur with increasing drainage area and are reflected by the species community at the site. Management models that currently incorporate ecoregions in the classification or prediction of stream ecosystem structure would benefit from the inclusion of specific components that incorporate drainage area measurements.[PUBLICATION ABSTRACT]