Caranx Ignobilis (Giant Trevally): ID, Size, Eating

Caranx ignobilis is the giant trevally, a large, heavy-bodied reef predator of the Indo-Pacific. Check these marks:

• Head: a steep, blunt forehead; the upper profile of the body is more curved than the lower one (Wikipedia).
• Colour: silvery grey, sometimes with scattered dark spots; large mature males can turn almost jet black (Wikipedia). There are no blue fins, which rules out the bluefin trevally.
• Tail scutes: 26 to 38 very strong, bony scutes along the straight rear part of the lateral line, in front of the tail (Wikipedia).
• Lateral line: a pronounced arch at the front, with 58 to 64 scales in the curved section (Wikipedia).
• Gill rakers: 20 to 24 in total on the first arch, counting rudiments (FishBase). This is how scientists confirm a fish in the hand.

For a photo ID, shoot the whole fish side-on with the fins spread, then take a close shot of the tail area so the scutes show. Record where you caught it: this species lives in the Indo-Pacific, so a big jack caught in the Atlantic is almost certainly something else.

The bluefin trevally (Caranx melampygus) shares reefs with the giant trevally across much of its range, and the two are the jacks most often mixed up. Wikipedia gives the differences:

• Fins: the bluefin has electric-blue dorsal, anal and tail fins; the giant trevally never does.
• Spots: the bluefin has many blue and black spots on its sides.
• Size: the bluefin reaches 117 cm but is rare above 80 cm, far smaller than a large GT.
• Hawaiian name: the bluefin is omilu, or blue ulua.

In Hawaii's 1998 records, anglers landed 704 pounds of bluefin against 10,149 pounds of giant trevally (Wikipedia). The giant trevally has also been confused in the past with the Atlantic crevalle jack (Caranx hippos), but the two live in different oceans; only two giant trevally have been documented in the eastern Pacific, off Panama and the Galapagos, in the 2010s (Wikipedia).

FishBase and Wikipedia both give a maximum of 170 cm (67 in) and 80 kg (176 lb). FishBase puts the common length at 100 cm, and Wikipedia notes that fish of 50 kg and above are not uncommon in sport fishing.

Growth and age: Wikipedia reports maturity at 54 to 61 cm, at three to four years old, and a growth model that puts a 1.7 m fish at around 24 years. FishBase gives maturity at 60 cm and a generation time of 13.7 years, and rates the species' resilience as low, with a minimum population doubling time of 4.5 to 14 years. That slow turnover is one reason many anglers release big fish.

Yes, toward prey, and occasionally toward people. Wikipedia describes the giant trevally as an apex predator that hunts alone and in schools, and records these behaviours:

• ramming blacktip reef sharks;
• leaping out of the water to catch fledgling sooty terns at Farquhar Atoll;
• following monk seals to steal their prey;
• a spearfisher in Hawaii who broke three ribs after being rammed by a giant trevally.

FishBase adds that it hunts crustaceans and fish mainly at night. Practical points: divers and spearfishers should not hold speared fish close to the body where GT are active, and anglers should use pliers and keep hands clear of the gill plates and the sharp tail scutes when unhooking.

Opinions on the taste range from poor to excellent, according to Wikipedia, but the bigger issue is ciguatera. Wikipedia reports numerous cases of ciguatera poisoning linked to giant trevally, and FishBase also lists reports of ciguatera. Wikipedia adds that since 1990 giant trevally from Hawaii have been barred from international auction sales because of these toxicity concerns.

We do not say any giant trevally is safe to eat. Check your local health authority's advice for the reef where the fish was caught. If anyone feels unwell after eating reef fish, contact a doctor or poison control (in the US, Poison Control at 1-800-222-1222) and say what fish was eaten. See our grouper page for another reef fish with the same concern.

Hawaiians call the giant trevally ulua, often with a prefix such as black, white or giant; Wikipedia notes it was historically held sacred and associated with a warrior's strength. The bluefin trevally is omilu.

Hawaii's Division of Aquatic Resources (DAR) sets these rules for ulua and papio, under HAR 13-95 (checked 25 September 2026):

• minimum size 10 inches;
• minimum size 16 inches to sell;
• bag limit 20, total for all species, non-commercial only.

Rules change; check the DAR regulations page before you fish.

Juveniles use estuaries, bays and lagoons and prefer turbid water; adults move to clear lagoons, seaward reefs and atolls, down to 188 m (FishBase, Wikipedia). Wikipedia notes a salinity tolerance of 0.5 to 38 ppt, which is why young fish can enter nearly fresh river mouths. FishBase says spawning happens on shallow seaward reefs and offshore banks.

The diet is mostly fish, especially parrotfish and wrasses, plus crustaceans, cephalopods and molluscs (Wikipedia).

The giant trevally is a popular sport fish, often fished catch-and-release (Wikipedia). Wikipedia gives Asian commercial catches of 4,000 to 10,000 tonnes a year between 1997 and 2007, a 1998 Hawaii catch of about 10,000 pounds, and an 84% decline in historical landings since 1900. FishBase rates its vulnerability to fishing as high to very high (74 of 100) and lists it as IUCN Least Concern (2015). FishBase also puts it in its high price category as a food fish.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices and rules are given with the date we checked them (25 September 2026); they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.