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Spatial distribution of a littoral fish community in a Canadian Shield lake: a multiscale analysis.

Brind'Amour, Anik *,1, Boisclair, Daniel1, Legendre, Pierre 1, Borcard, Daniel1, 1 Université de Montréal, Montreal, QC, Canada

ABSTRACT- Many studies have been done to develop relationships between measures of fish assemblage and environmental characteristics. However, the identification of the proper spatial scale(s) at which the existence of such relationships should be tested, and the relative significance of processes occurring at these scales remain key problems of habitat models. Our study aimed to assess the spatial patterns of littoral fish assemblages displayed at different scales and to identify the environmental factors that are structuring the fish assemblages at each of these spatial scales. This was done using a new statistical tool, Principal Coordinates of Neighbor Matrices (PCNM), that detects and quantifies patterns over a wide range of spatial scales. The fish community exhibited scale-dependent variability that we grouped into four submodels ranging from 1500 m (very broad scale) to less than 100 m (fine scale). These scales were associated to specific environmental variables, suggesting the presence of scale-dependent ecological processes within the lake. Functional groups of species were viewed in a spatial context according to the range of spatial scales to which they were associated. Our study provides a quantitative support to the perspective that the littoral zone of lakes should be perceived as a hierarchical arrangement of habitats that differ not only by the environmental conditions among them but also by the spatial scales at which environmental conditions vary within them.

Key words: Fish community, Littoral zone, Multiscale, Spatial analysis

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