Between‐year variation in community structure and biomass–size distributions of benthic lake fish communities

The benthic fish communities of 26 Swedish lakes were monitored annually with multi‐mesh gillnets in a standardized way in the years 1994–1997. No major environmental changes (e.g. in nutrient level or acidity) occurred within the lakes during the 4 years of study. In most of the lakes, the between‐year variation of biomass (per unit of effort) was close to the sampling precision, and biomass was usually less variable than abundance. Median values of lakespecific indices of variance compensation indicated no general covariance of biomass between species, but a tendency for positive covariance between size classes. This indicates that the benthic fish communities of small to intermediate‐sized Swedish lakes most often show low between‐year variation in total biomass of fish older than 0+, and that their biomass–size distributions are not, in general, shaped by periodic strong year‐classes of keystone species. In a few individual lakes, density compensation was indicated as complementary proportions of a pair of species or size classes that made major contributions to the total biomass.