Crevalle Jack

The crevalle jack is a powerful predatory fish which predominantly takes other small fishes as prey at all stages of its life, with various invertebrates generally being of secondary importance to its diet. Several studies conducted on the species diet over its range have found other aspects of its diet vary widely, including the specific types of prey the species takes and the change in diet with age. The most detailed of these studies was conducted in the southern states of the USA, which showed that the species diet comprised between 74%% and 94%% fish. The remainder of the diet was various prawns, shrimps, crabs, molluscs and stomatopods. The types of fish taken varied throughout the range, with members of Clupeidae, Sparidae, Carangidae and Trichiuridae all taken in variable amounts, usually with members of one family dominating the local diet. The percentage of various invertebrates also was highly variable, with penaeid shrimps, portunid crabs, stomatopods and squid being of importance to different populations. The study also indicated young crevalle jack predominantly take clupeids, adding sparids and later carangids to their diet as they grow larger. The larger individuals also took much higher amounts of invertebrates, and also small quantities of seagrass, indicating larger fish are more opportunistic. This general change in diet with age also seems spatially variable, with young crevalle jack in both Maryland and Puerto Rica consuming almost exclusively crustaceans including shrimps, crabs (and juvenile tarpon) in Maryland and harpacticoid copepods in Puerto Rica before moving to fish dominated diets later in life. Research in Ghana shows a pattern somewhat intermediate to the previous two locations; adults take larger fish, predominantly Engraulis guineensis and Sardinella eba, while juvenile fish take smaller fishes such as Epiplatys sexfasciatus or juvenile caridian and penaeid shrimps.