The effects of temperature on feeding in zooplanktivorous walleye,Stizostedion vitreum, larvae

Abstract

We examined the prey capture process in walleye larvae (9.8–18.0 mm mean length) feeding on zooplankton (density 1501−1) in laboratory aquaria at 15,18.5 and 22°C. Larvae were starved for ≥8 h prior to the experiment and only allowed to feed for ≤10 min during the experiment in order to minimize the influence of gut processing or satiation on feeding behaviour. Prey consumption (μg min−1) increased exponentially and prey capture success (%) increased logarithmically with mean walleye length. Prey consumption and attack rate (strikes min−1) increased significantly with increasing temperature. The effect of temperature on capture success was slight (2% increase from 15 to 22°C) and not significant. Walleye showed positive electivity for medium-sized prey (0.3–0.6 mm body width, mostlyCeriodaphnia quadrangula), negative electivity for small prey (≥0.3 mm, mostly cyclopoid copepods) and neutral electivity for large prey (≥0.6 mm, mostlyDaphnia sp.). Neither prey species electivity nor prey size electivity were significantly affected by temperature. However, prey size electivity did show a fairly large effect size with respect to temperature and we suggest that this relationship should be examined further. These results indicate that temperature affects prey capture in walleye larvae primarily by influencing attack rate.