The giant trevally (Caranx ignobilis), is a species of fish belonging to the Jack/Carangidae family. It is also known as ulua in Hawaiian, mamulan in the Marianas, rōnin-aji ("ronin jack") in Japanese, and "GT" in many places, the giant trevally has many local names.
Giant trevally are robust and solid in appearance and can be
recognised by a steep and blunt head profile. They have immense power
which can be attributed to thick shoulders and midsections of muscle
and large almost paddle-like pectoral and tail fins.
Colouration can range from an almost white-silver to jet black. They
may also exhibit a dusky golden hue all over the body, particularly on
the fins. The giant trevally lacks a dark spot/colouration on the operculum (found behind the eye).
In addition to the body colour of the giant trevally, striking
striations and markings on the top section of the fish may also be
present, particularly on the back. This is generally seen when the fish
has a much darker back than the rest of the body, the contrasting
markings showing up as light silvery lines. Black dots a few millimetres in diameter can also be found scattered all over the body, coverage can vary between none, sparse and widespread.
Scutes (small sharp plates) exist along the posterior portion of the lateral line
and proceed along to the tail. Caution is recommend when holding a
giant trevally due to the sharp scutes which can inflict significant
Giant trevally distribution is widespread, existing in the warm tropical waters of the Pacific and Indian Oceans. They are usually found as far south as central New South Wales in Australia, east to the Hawaiian Islands, west to the eastern islands of Africa and north to Japan.
Habitat ranges from estuaries to coral reef
systems. Juveniles tend to be more prevalent in estuaries and river
systems. Larger specimens move out to deeper water where there is
usually structure such as a coral reef, bombora or drop-off/channels.
Strong currents are usually present where these deepwater environments
exist. They will also venture onto flats, headlands and shallow water
to hunt food. Giant trevally can also be found along the reef edge and
points where large pounding swells crash on the reef and rock stirring
up food and creating the ideal environment to hunt.
The giant trevally uses its superior swimming abilities and power to
hunt and smash baitfish. If the giant trevally doesn't engulf the prey
within the first strike, the prey is usually stunned or dead from the
strike impact. They will usually devour the prey quickly with one bite
as competition can be fierce from other specimens in the pack.
Just about any baitfish (small fish) existing in tropical waters is
in the giant trevally diet. Species of fusiliers from the Lutjanidae
family seem to be particular favourites of the giant trevally. There
have also been reports of juvenile turtles & dolphins being found
within the stomach contents of larger giant trevally.
Large giant trevally can also be found in the presence of large reef
sharks as they use the shark as a tool to ambush prey. Large giant
trevally have also been known to eat other smaller giant trevally and
reef fish when the smaller fish is hooked by an angler.
Giant trevally mature at around the ages of 3 or 4 years, they are generally around 60 cm in length. This indicates that the giant trevally is a very fast growing fish.
Large, usually solitary specimens can reach over 200 lb and be around 1.7 metres in length.
It is not known whether there is a ratio or abundance of what gender when it comes to larger more dominant specimens.
Information from Wikepedia -http://en.wikipedia.org/wiki/Giant_trevally