Larval condition and vulnerability to predation: an analysis based on mixed-prey experiments

Abstract

Many recent studies in larval fish ecology measure larval nutritional condition (e.g., RNA/DNA ratios), with the ultimate goal of assessing future survival probabilities. Larvae of intermediate or poor condition are generally considered to be more vulnerable to predators than larvae in good condition. The objective of our study was to experimentally test whether larvae in poor condition have lower relative survival rates when exposed to a predator. We conducted mixed-prey experiments with larval capelin (Mallotus villosus) on days 6, 8, and 10 posthatching by putting 75 fed and 75 starved larvae in 38-L containers with (treatments) and without (controls) predators (juvenile lumpfish, Cyclopterus lumpus). There were no significant differences in the mean condition (RNA/DNA ratios) or dry weights of larvae recovered from controls and treatments. These results suggest that RNA/DNA ratios are not useful indicators of vulnerability to predation for larval capelin.