The influence of prey identity and size on selection of prey by two marine fishes

Laboratory experiments were conducted with two predatory fishes, Lagodon rhomboides (Linnaeus) and Syngnathus floridae (Jordan & Gilbert), to determine if prey selection was a result of predator preference or prey accessibility. Prey consisted of two species of caridean shrimp, Tozeuma carolinense (Kingsley) and Hippolyte zostericola (Smith), that commonly inhabit seagrass meadows. Natural diets of both predators revealed that selection ofTozeuma and Hippolyte was not related to their field densities. My experiments demonstrated that natural prey selection was a consequence of prey accessibility, not predator preference. Experiments examining the role of prey size in predator preference revealed that large individuals were significantly preferred over small individuals. Observations of prey behavior indicated that prey motion affected predator choice. These results suggest that predator preference was primarily determined by prey visibility and that the combined effects of prey size and motion contributed to the visibility of these prey.