Biomechanical limits to ecological performance: mollusc-crushing by the Caribbean hogfish, Lachnolaimus maximus (Labridae)

Functional limitations on feeding ability were investigated in the mollusc-crushing Caribbean hogfish, Lachnolaimus maximus (Labridae). Two constraints were proposed to limit the maximum size prey L. maximus can eat: pharyngeal jaw gape and crushing force. These factors yield diflferent quantitative expectations for the relationship between fish size and maximum prey size. Their relative importance for predation on a frequently consumed gastropod ( Cerithium litteratum ) was investigated in laboratory performance tests designed to determine the largest snails fish could eat. Cerithium predation was found to be force limited rather than gape limited. The importance of this functional constraint in determining the largest Cerithium consumed by wild fish was examined by comparing hogfish feeding capability, as determined by the performance tests, to the maximum size snails found in the stomach contents of field-collected fish. Crushing ability appears to limit Cerithium predation in natural fish populations. The utility of performance testing for determining the functional and ecological importance of morphology is discussed.