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USE OF COLD FLOODPLAIN MARGIN HABITATS BY A STREAM FISH ASSEMBLAGE
Citation:
Ebersole, J L., W. J. Liss, M. Szedelyi, AND T. Guy. USE OF COLD FLOODPLAIN MARGIN HABITATS BY A STREAM FISH ASSEMBLAGE. Presented at Oregon Chapter of American Fisheries Society, Sunriver, OR, February 26-March 1, 2002.
Description:
We studied the effects of temperature and other habitat characteristics on fish assemblages and their distribution among coldwater patches potentially functioning as "coldwater refugia" for salmonids. Potential coldwater refugia in alluvial segments of the Grande Ronde River of northeast Oregon were intensively sampled for fish July-early September 1997, 1998 and 1999 concurrent with measurements of physio-chemical characteristics of coldwater patches. Discrete fish assemblages within coldwater patches were identified through multivariate classification and ordination and correlated with environmental characteristics that differed significantly between assemblage groups. Coldwater patches with fish assemblages characterized by catostomids (bridgelip sucker Catostomus columbianus and largescale sucker C. macrocheilus) were significantly more isolated from mainchannel habitats, had lower amounts of riparian canopy density, and had higher specific conductance than coldwater patches dominated by salmonids (Rainbow trout Oncorhynchus mykiss, and chinook salmon O. tshawytscha; ANOVA P<0.05). Coldwater patches with assemblages comprised largely of cyprinids (mostly redside shiner Richardsonius balteatus and northern pikeminnow Pteichocheilus oregonensis) were intermediate with regard to isolation, canopy density, and specific conductance. Physical coldwater patch characteristics contributing most frequently to logistic regression models of patch use by salmonids included metrics related to alcove depth, temperature, specific conductance, canopy density, suitable coldwater patch volume, and coldwater patch location (adjacent riffle or pool mesohabitat). These results suggest that suitability of potential thermal refugia for salmonids among our study sites may be influenced by factors related to refuge and channel morphology and adjacent riparian conditions.