The Life Cycle of the Giant Trevally
During the week I took the opportunity to head out on a night fishing expedition in the turbid waters of Darwin Harbour. I can report that apart from a plague of small sharks the only decent catch was a 14kg Black Jewfish.
Now I know what you are thinking - yes I did write a post on the plight of the Black Jewfish but this was caught on a charter boat with paying passengers and I was not the one who hooked it.
Interestingly, the charter boat used straight hooks and the fish was hooked in the gut. The depth of the water was around 15 metres and this combination would appear to have stacked the odds against the poor old fish even if it was let go.
I also discussed the aspect of aggregation and territorialism with the crew and they believed this to be a good thing as it meant that they could rely on the black jewfish being around for their customers.
Ok, enough of that - this week I will discuss one of the monsters of the sea; the Giant Trevally (GT’s) or Caranx Ignobilis (sounds like an ex Roman Emporer). They are the largest of the Carangidae family that boasts members such as the Queenfish, Amberjack and other Trevallys.
These fish are spread from Japan to Australia, East Africa to Hawaii in warm tropical waters in both the Pacific and Indian oceans.
GT’s reach sexual maturity between the ages of 3 and 4 at a time when they are around 60cm in length. Interestingly males outnumber females.
Spawning takes place during the summer months on shallow seaward reefs or offshore banks and the resultant larvae is thought to head to open waters.
At age one the GT’s are around 20cm in length and juveniles and young adults spend time schooling in turbid inshore, lagoon or estuary areas feeding during the day time.
Once they reach about 40cm they will head out to reef areas, channels or inhabit inshore sand flats.
Large adults are solitary predators often guarding clear lagoons or seaward reefs to a depth of 80m and feeding on crustaceans and other fish at night.
These huge GT’s can live to 15 years of age, weigh in at 60Kg and reach lengths of 1.7
Next week I’ll discuss the life cycle of a fish that comes complete with its own thumb print!
Until then…
Sea you later,
Skipper Meggs