Influence of turbidity on piscivory in largemouth bass (Micropterus salmoides)

In situ and laboratory feeding trials coupled with stomach content analysis of largemouth bass (Micropterus salmoides) were performed to examine how turbidity influences the size selectivity and capture rates of prey. No significant differences in the capture success of adult largemouth bass preying on northern redbelly dace (Phoxinus eos) were observed during in situ feeding trials in two Lake Ontario coastal wetlands differing in turbidity level (2.3 and 20 nephlometric turbity units (NTU)). During 1-h laboratory feeding trials, the overall number of fathead minnows (Pimephales promelas) captured was not significantly different among 1-, 18-, and 37-NTU treatments. However, at 70 NTU, the number of fathead, minnows captured was significantly lower than that at the lowest turbidity treatment. Selection by juvenile largemouth bass of the smallest size-class of fathead minnow decreased as turbidity increased. No significant differences in piscivory were apparent between juvenile largemouth bass collected from turbid and clear habitats. Stomach content comparisons of juvenile largemouth bass seined from six clear and turbid habitats suggest that piscivory is primarily regulated by the availability of vulnerable size-classes of prey fish, as opposed to water clarity.