Factors Related to the Biomass and Production of Fish Communities in Small, Oligotrophic Lakes Vulnerable to Acidification

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We estimated biomass and production of the fish community in 19 small (<50 ha) lakes from four watersheds in central Ontario. Lake pH ranged from 4.8 to 7.1. We found 19 fish species in these lakes; yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), white sucker (Catostomus commersoni), and largemouth bass (Micropterus salmoides) were the most common. On average, there were 4.5 species per lake. Neither fish community biomass nor production was significantly different among the communities identified by cluster analysis, and the number offish species was not lower at lower pH. More than 75% of each lake's total biomass was confined to less than three fish species. Whole-lake fish biomass was related to the total number of species in the lakes and their average age. Fish community production was related to fish biomass, averge fish size, and acid neutralizing capacity (ANC) with an almost equal influence provided by each factor. At lower ANC and pH, fish were usually smaller in weight and often had lower population growth rates. In these lakes where the influence of lake size and trophic status was minimized, fish community biomass and production were only secondarily related to lake pH or ANC.