Crevalle Jack - Biology and Ecology

Biology and Ecology

The crevalle jack is one of most abundant large carangids in the Atlantic Ocean, with at least two systematic studies placing it within the top five most abundant species of that region, namely lagoons in Nigeria and Chiapas, Mexico. Seasonal movements are known from both the American and African coastlines, with both juveniles and adults appearing to migrate. In North America, young individuals recruited to northern estuaries are known to move to warmer tropical waters at the onset of winter to escape possible hypothermia. At least one hypothermia-driven mass mortality of 200 crevalle jacks has been reported from the Slocum River in Massachusetts, indicating low-temperature mortality is a major concern for north-ranging groups of the species, with temperatures below 9.0°C apparently being lethal to the fish. This applies not only to river dwelling fish, but also to marine migrants which linger too long in the temperate regions during winter. In Nigeria, and presumably other parts of Africa, the species appears to migrate seasonally, possibly to take advantage of prey, with the fish arriving in Nigeria during September to November. The species is more active during the day than the night, with larger catches in fisheries taken during the day, also. The crevalle jack is a schooling species for most of its life, forming moderately large to very large, fast-moving schools. At larger sizes, the fish become more solitary and move to the deeper offshore reefs. Evidence from laboratory studies indicates crevalle jack are able to coordinate their feeding and spawning aggregations over coral reefs based on the release of dimethylsulfoniopropionate (DMSP) from the reef. DMSP is a naturally occurring chemical produced by marine algae and, to a lesser extent, corals and their symbiotic zooxanthellae. Field studies have also shown the species increases in abundance with increased levels of DMSP over coral reefs.