The effects of turbidity and an invasive species on foraging success of rosyside dace (Clinostomus funduloides).
Habitat degradation and biological invasions are important threats to fish diversity worldwide. We experimentally examined the effects of turbidity, velocity and intra- and interspecific competition on prey capture location, reactive distance and prey capture success of native rosyside dace (Clinostomus funduloides) and invasive yellowfin shiners (Notropis lutipinnis) in Coweeta Creek, North Carolina, U.S.A. Increased turbidity and velocity produced significant decreases in the number of prey captured forward of the fish's location. It is possible that this represents an increase in the amount of energy expended per prey captured. We used Akaike's Information Criterion (AIC) to evaluate competing explanatory models for reactive distance (10 generalised linear models, GLM) and prey capture success (9 generalised linear mixed models, GLMM). Reactive distance decreased by 12% with an increase from 2 to 4 conspecifics, whereas a 10 NTU increase in turbidity reduced reactive distance by 9%. Capture success was affected by velocity, dominance and competition, and varied among species. A 6 cm s-1 increase in velocity produced a 28% decline in capture probability; however, dominant fish were 3.2 times more likely to capture a prey item than non-dominant fish. Yellowfin shiners only were 0.62 times as likely to capture a prey item as rosyside dace. Both intra- and interspecific competition reduced capture probability, and fish in high density intraspecific or interspecific trials were 0.46 times and 0.44 times as likely to capture prey, respectively, as fish in two fish intraspecific trials. These results suggest behavioural variables are as important as physical factors in determining reactive distance and capture probability by these minnows.