Characterization of littoral fish assemblages and their habitat in the St. Lawrence River near Cornwall, Ontario.

Characterization of littoral fish assemblages and their habitat in the St. Lawrence River near Cornwall, Ontario.

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Title: Characterization of littoral fish assemblages and their habitat in the St. Lawrence River near Cornwall, Ontario.
Author: Ribey, Sandra Carolyn.
Abstract: This project was aimed at (i) characterizing and comparing littoral fish communities upstream and downstream of the Moses-Saunders hydroelectric dam on the St. Lawrence River near Cornwall, Ontario and Massena, New York and (ii) exploring relationships between habitat characteristics (including depth gradient--the distance from shore to a 1m depth, percent aquatic vegetation, and percent substrate type) and fish community characteristics (diversity, abundance and biomass). A total of 74,419 fish (43 species) were captured in 36 sites (14 upstream and 22 downstream) using a standard sampling protocol in 1994 and 1995. The downstream region (western portion of Lake St. Francis) had significantly higher number of fish species and biomass when compared to the upstream reservoir (Lake St. Lawrence). A clustering analysis of a Jaccard similarity matrix based on the presence-absence of species for each site revealed largely distinct interregional fish community composition with relatively homogeneous intra-regional communities. A principal component analysis (PCA) of fish species caught in 60% or more of sites allowed the definition of the main fish assemblages. The downstream fish community was characterized by a high abundance of Notropis volucellus, Fundulus diaphanus and Notemigonus crysoleucas, where as upstream a high abundance of Pimephales notatus was found. A PCA of habitat variables revealed a dispersal of downstream sites throughout the graph. The upstream sites clustered together. This suggests a broad spectrum of habitat types downstream, while upstream is more homogeneous. Regression and correlation analyses found relationships between fish variables and habitat variables. The downstream area had a wider variety of habitat types, as well as the higher percentage of vegetation cover, boulder and gravel, which supported a more diverse and abundant fish community.
Date: 1997
URI: http://hdl.handle.net/10393/4362

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