Golden Trevally - Biology and Ecology

Biology and Ecology

The golden trevally is found either as a solitary individual or in small schools as an adult. Juveniles tend to form larger schools which tend to congregate and follow ( or "pilot") larger fish such as groupers, sharks and even jellyfish. This behaviour mimics that of the related pilot fish, Naucrates ductor, with their maneuverability protecting from their host which in turn provides them with protection from predation from other fish. This behaviour extends to scuba divers, with one diver reporting a single young individual obsessively stationing itself in front of his face plate.

The golden trevally is a diurnal foraging carnivore which, unlike other carangids, does not normally seek out individual prey items. The highly protractile mouth possessed by the species is used to form a tube to suck prey out of both reef and algae dominated habitats as well as filtering organisms out of sandy substrates. In the former case, both sand and any prey items are taken into the mouth and filtered through the gill rakers; sand is expelled, while small organisms are trapped and swallowed. The species takes a variety of prey including crustaceans such as shrimps, crabs and amphipods, as well as molluscs and small fish. Golden trevally found inhabiting a mangrove swamp were found to have fed exclusively on fish (Mugil curema), suggesting the species also actively hunts down fleeing prey. A laboratory study utilising only four individuals being fed found that one fish will take the 'lead' position in this situation while another will attack the other fish in the school, apparently in competition for food.

A variety of parasites have been recorded from the species, including copepods, flatworms, and a nematode which inhabits the fish's swimbladder.

Reproduction in the golden trevally has been studied in both the Indian and Pacific Oceans. In the Pacific this was in Hawaii, where it was found spawning occurred from late February to early October, with a peak from late April to early September. Five distinct peaks during this time were correlated with the first and third quarters of the moon. Spawning occurred from the early evening into the night. In the Indian Ocean, the research was conducted in southern Persian Gulf. Here it was found spawning occurred in April and May, with defined peaks in recruitment of juveniles into the local fishery during September and October. The male:female sex ratio in this population was 1:1.01, close to parity. Growth rates were also studied using otoliths in this population, with an increase in growth rate during the winter months (November to April). Von Bertalanffy growth curves were also calculated for the species.