Biomass Size Spectra As Ecological Indicators Across Broad Environmental and Anthropogenic Gradients

Biomass size spectra (BSS) provide a means of summarizing fish community production. In lakes, abundance decreases as body size increases, that is, larger species such as Walleye are less abundant than the smaller species they forage upon such as Cisco or minnows. This relationship represents the underlying processes of energy transfer and predator-prey dynamics, which determine the abundance of taxa at different trophic levels. It approximates community production and the slope can be used to document impediments to production. This study evaluated the utility of BSS as an ecological indicator of community health and fisheries production in hundreds of lakes throughout Ontario. The relative influences of lake and watershed characteristics, community composition, climate and anthropogenic stress including exploitation on BSS were also determined. A general linear model indicated that BSS were related to lake morphometry, angler activity, climate, the presence of large predators and aquatic invasive species and water quality. Identification of regional patterns in BSS and an understanding of the factors influencing BSS will improve our ability to manage fisheries across large spatial scales.