Predator/Prey Dynamics of Micropterus salmoides, Gambusia holbrooki, and Non-Native, Small-Bodied Fish

One of the most influential factors on the life history of aquatic animals, such as teleost fish, is the risk presented by predators.  Despite the large number of exotic fish introductions in peninsular Florida, the freshwater systems have proven highly resistant to small-bodied, (< 150 mm in length) non-native, ornamental species, with a single exception in the African jewelfish Hemichromis letourneuxi.  Small-bodied fishes generally cannot employ one of the most successful methods for avoiding predation, large body size, because they do not grow enough to be immune to gape-limited predators.  We evaluated several representative non-native, freshwater, ornamental fishes’ vulnerability to two species of common, native predatory fish in tank experiments.  The non-native ornamental species, which functioned as prey in our system, were the African jewelfish, the kenyi cichlid Maylandia lombardoi, and the fancy guppy Poeciliia reticulata.  The native predators were largemouth bass Micropterus salmoides, a large-bodied predator, and eastern mosquitofish Gambusia holbrooki, a small-bodied but aggressive competitor and predator. We exposed sets of ten prey fish to three predator treatments (n = 4) including each predator alone (either 1 bass or 75 mosquitofish) and both predators together. We found that different predator treatments showed significantly different effects on prey fish mortality and caudal fin damage.  We also examined their behavior on the first and last day of the trial, as well as in a series of short-term observation tank trials.  The predators interacted with each other as well as the prey fish in the combination treatment. These data support the hypothesis that native predators can reduce the probability of establishment by ornamental fish in Florida.