Growth, abundance, and food supply of white sucker

Twenty-three populations of white suckers Catostomus commersoni from Ontario lakes were investigated to determine if growth was density-dependent and if the abundance of chironomid larvae in the lake littoral zone was an important factor influencing growth. White sucker population sizes were estimated with either the Petersen mark-recapture or the catch-per-unit-effort method. White sucker fork length at age was back-calculated from the first pectoral fin ray. Each take was divided into three thermal zones based on the position of the thermocline, and the benthos was quantified from 60 core samples prorated over the three zones. Canonical correlation and redundancy analyses indicated that the abundance of benthos, especially chironomids in the littoral zone, was a good predictor of white sucker growth. Growth was not so important in explaining benthos abundance. Regression and correlation analyses indicated white suckers from lakes with more abundant chironomid larvae in littoral zones and low white sucker population densities tended to increase in length faster than white suckers from lakes with less abundant littoral chironomid larvae and high white sucker population densities. Significant negative correlations were found between white sucker population size and abundance of measured benthos. This study provided the first evidence that white sucker growth may be constrained by both population density and food supply.