Ask Dr Dazza: Identifying javelin fish

Moreton Bay has a wonderfully diverse array of fish for the recreational angler to catch, but this can lead to problems for anglers to correctly identify them and know the correct size and bag limits.

It is common for anglers to rely on social media for fish identification, but the responses received are not always correct.

In a previous column, I discussed the subtle physical differences between grass sweetlip and spangled emperor, both which are caught in Moreton Bay.

Let’s move on to javelin fish or as they are also called grunter bream. They frequently “grunt” on capture – hence one of their common names.

There are two species that occur – the barred javelin fish (Pomadasys kaakan) and the small spotted javelin fish (Pomadasys argenteus). Anglers unfamiliar with them frequently mistake them for yellowfin bream. While they are both the general shape of the common yellowfin bream, they differ by having a square tail.

Of the two species of javelin fish, the spotted javelin fish is more common and widely distributed in Moreton Bay. They can be found in the upper reaches of rivers and creeks although they can aggregate in downstream areas – particularly after rain events. Large examples of barred javelin fish can turn up at places like Mud Island.

As their names suggest, small spotted javelin fish are covered by a series of small spots across their sides, while the barred javelin fish has spots arranged in a series of distinct wide vertical bars.

Barred javelin fish grow substantially larger than spotted javelin fish and both species have different legal sizes. The small spotted javelin fish has a minimum legal size of 30cm whereas the barred javelin fish has a minimum legal size of 40cm. Therefore, it is important to be able to tell the two species apart! Failure to do so risks a fine for keeping an undersized fish if the 35cm javelin fish you retain happens to be a barred javelin fish.

Local anglers also confuse fingermark bream (Lutjanus johnii) with Moses perch (Lutjanus russelli). To further confuse things, a second species of Moses Perch (Lutjanus fulviflamma) more typically found further north is becoming more common in Moreton Bay – at least where I fish.

These species along with many others have a “false eye spot” which is thought to be a visual adaptation to reduce predation risk. The false eye spot is usually bigger than the fish’s actual eye. Although I have seen a couple of actual juvenile fingermark bream in Moreton Bay in my over 35 years fishing, if you catch what you think is fingermark bream in the Moreton region there is a 99.9 per cent chance it is a Moses Perch.

Tight lines everyone, but make sure you know what was on your line before you keep it!