Giant trevally

How it lives

Juveniles use estuaries and murky coastal water. Adults live on clear lagoon and outer reefs, down to about 188 m. Mature fish are mostly solitary, but they form groups to feed and to spawn. They mature at about 60 cm and around 3 years of age. Growth curves suggest a 1 m fish is about 8 years old and a 1.7 m fish about 24 years old. Spawning takes place on shallow outer reefs and offshore banks in the warmer months, timed to the moon.

Where it goes

Adults tend to stay in a home range of up to about 9 km, while juveniles can travel about 70 km to outer reefs. Larger seasonal trips seem to be made to gather at spawning sites. No migration route is described in the sources read for the Cook Islands.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

Global: Least Concern on the IUCN Red List, assessed in 2015. Large fish are heavily targeted by small-scale and recreational fisheries across the range, and big adults can carry ciguatera toxin (FishBase). Hawaii: giant trevally are described as severely depleted in the main islands, where they make up under 0.03 percent of apex predator biomass in fished areas, against 71 percent in undisturbed ecosystems. Cook Islands: no local population count was found. Marae Moana, created by law in 2017, covers the whole 1.9 million square kilometre ocean zone, with protected areas covering 16 percent of it, plus traditional ra'ui harvest bans decided by each community.