Until recently, jacks larger than 50 cm were considered relatively rare in rivers and estuaries. More recently, however, it has become clear in places like SE QLD that there may be more trevally in our rivers than previously thought. This awareness was accompanied by improvements in bait and fishing technology that allowed anglers to effectively target larger fish (usually for catch-and-release and release) – in previous years, it was hard to tell how many 50+cm jacks remained in estuaries because fish of this size were extremely difficult to get out of their hooks! Like other lutjanids, jacks do not change sex during their lifetime and can take between four and eight years to mature between 40 and 50 cm, depending on water temperature and food availability. This means ensuring that enough trevally survives to reach the reefs offshore. Catching and releasing caught river fish is therefore considered an important management option by many of the trevally specialists involved. The maximum size of mangrove trevally on offshore reefs exceeds one meter in length and 16 kg, and it seems that jacks about 70 to 80 cm in length can be between 15 and 30 years old. Secondly, the moon has a great influence on mangrove trevally, which become increasingly active with different moon phases for different reasons. The new moon is a good time because shrimp run overboard in dark nights, and jacks love shrimp. They are highly mobile and tend to rise and travel with larger tidal currents, i.e. the morning tides of the new moon and the evening full moon.
To support their predatory activities, they have distinctive canines at the front of the mouth, which are suitable for catching and holding their prey. Large, highly pointed canines are an unmistakable trademark of lutjanids and deserve respect as they can cause careless injuries. Mangrove mackerel is found throughout much of the tropical Indo-Pacific and has been reported in places as far away as Samoa, throughout Asia, off the coasts of India and East Africa, and even as far away as the Mediterranean Sea (probably via the Suez Canal). In Australia, trevally can be caught along our north coast, from Broome in the west to the rivers of the central coast of New South Wales. South of Fraser Island, these are more seasonal catches and can only be reliably targeted during the summer months when water temperatures approach or exceed 22°C. Simply put, the universal technique is to take a bite, hang your jack, and then pull it as if your life depended on it. However, there is an important difference between the southern and tropical fisheries, as the frequency of trevally in southern waters is much lower than in the north, meaning that fishing in southern waters can be more reliable with live bait than with bait. If you know for sure where jacks stand, then fishing the place with bait is the most likely way to join.
However, the tide turns in favor of bait fishing when trying to find a trevally, as a slow drift is perfect for peppering an area with bait. Bait fishing allows a fisherman to fish an area much larger than the bait. These large 80cm+ trevally were caught in reefs off the coast of northern Papua New Guinea. Image: Ben Diggles And that, ladies and gentlemen, is the appeal of mangrove trevally fishing in the subtropics; You`ll never land all the fish on the hook, but it`s a lot of fun and there`s always a chance to meet a monster! Structure is essential when targeting trevally. They prefer a shady, complex structure that allows them to cram tightly, often in small schools. In brackish streams and estuaries, this means submerged wood and crushed rock, and you can add bridge and jetty pylons and rock faces in more general estuaries. In the past, I found jacks in a pile of car bodies and concrete pipes that had been pushed into the river, and in another where a dead cow was caught in a pile of logs. Hard to go down, but lots of connections! Success multiplies when fishermen succeed, and to get it right, you have to appreciate three different factors, the first of which is the temperature of the water.
Although the cylinders can survive in water up to 15 ° C, they are quite closed in an almost catatonic state. To become active again, they must warm up and become the feeding and fighting machines that characterize the mangrove trevally as the main recreational species – hot water at 22°C is the door. Thus, late spring or early summer are reliable times to start trevally fishing, although cold water currents still stop them.
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