Yellow Perch (Perca flavescens) Biomass Responses to Different Levels of Phytoplankton and Benthic Biomass in Lake Memphremagog, Quebec–Vermont

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Abstract
Perch biomass in Lake Memphremagog, Quebec was 2.5 times greater in the more productive south than in the less productive north basins. This difference is on the same order of magnitude as biomass differences in the phytoplankton (approximately 1.6×) and benthic (approximately 3×) communities. The difference in perch biomass is attributed to a larger perch population in the south basin. Growth was similar in both basins, and therefore independent of production at these lower trophic levels. Perch growth in both basins is maximal for the Quebec area and probably controlled by the length of the growing season. Abundance levels are fixed by the fourth year and possibly prior to reaching the second year of life. Perch biomass responses to different food levels in Lake Memphremagog provide empirical support to Moore’s (1941) suggestion that at abundant food levels, population size and not growth is enhanced. Previous experiments defining the relation between growth and nutrient concentration and/or primary production did not fully represent the situation in Lake Memphremagog. This may have been due to conditions in simple, controlled systems not usually found in natural, complex ones.

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