Fish Facts

FISH FACTS: Australian permit (Trachinotus blochii)

Image: Scott Thomas

FOR many years Australian anglers, particularly fly fishers, were teased and tempted by glossy international flyfishing magazines containing stories of challenging encounters with permit. Even as recently as 20 years ago, the media spotlight for flats fishers was firmly on the “true” permit Trachinotus falcatus of Atlantic and Caribbean fame.

But time has moved on and today Aussie anglers need not feel deprived of permit action anymore. Indeed, we’re the lucky country in that we have not just one, but two species of permit in Australian waters which are equally challenging, and at least one of them has a growth potential comparable to their US cousin.

The snub-nosed dart, aka Tropical permit, aka Indian Ocean permit Trachinotus blochii, was the first of the Aussie permit species to be described. Way back in 1801 the famous French naturalist Bernard Lacépède called it “Caesiomorus blochii”, but this was done to correct the first scientific mention of this species by Swedish naturalist Peter Forsskål, who incorrectly described it as the Atlantic permit (then known as Scomber falcatus) in 1775.

The fact that early naturalists had trouble telling these species apart shows the morphological differences between the Australian permit species and the “real” Atlantic permit are quite small. The local species has slightly longer anal and dorsal fins with yellow colouration and black edges, a rounder head and shorter mouth, but otherwise appear virtually identical to Atlantic permit.

We now know Trachinotus blochii is widely distributed, occurring throughout the Indo-Pacific region from the East coast of Africa as far north as Japan, throughout tropical northern Australia and as far east as the Pacific coast of central America. In Australia T. blochii can be encountered near tropical sandy beaches and sand flats from north of around Geraldton in WA across the top end and south to around Brisbane, as well as Lord Howe and Norfolk Islands.

On paper Atlantic permit appear to edge out T. blochii in maximum size, with the growth potential of T. falcatus exceeding 120 cm and 30 kg. In comparison, most reference works list T. blochii as topping out at 110 cm and around 16 kg. Relatively little is known about the growth rates or breeding of wild T. blochii, however, the species is widely farmed in South East Asia (particularly in Taiwan) where it grows rapidly, reaching 5 cm after only 35 days from hatching.

But that is not the end of the Aussie permit story. During the heyday of oyster farming in the late 1800s and early 1900s in Queensland, oysterers working in Hervey Bay noticed their leases being plundered by schools of large fish which “pick up the oysters while standing on their heads , as it were, with the tail near the surface, and are often 6 ft in length”.

Schools of these “oyster cracker” fish would reportedly take heavy toll of newly laid out juvenile oyster spat, and were considered the scourge of oyster farmers in central and southern Queensland at the time. A notice in the Brisbane Courier in November 1907 (reproduced in full at the end of this article to show how much journalistic standards have slipped over the past 100 years) detailed how several metre plus long specimens were eventually procured and sent to Brisbane for identification. Here they were examined by ichthyologist J. Douglas Ogilby who recognised them as a new species within the trevally family, having plain yellow lower dorsal and anal fins which lack the black edges that are prominent in T. blochii.

By 1909 Ogilby had described the oyster cracker dart as Trachinotus anak “a large fish destructive to oysters”. More recent scientific work has confirmed T. anak is indeed a separate species, based on skeletal differences. Indeed, as noted in previous fish facts, bony lumps on the skeleton (hyperostosis) are well described in several species of permit, including T. anak which, like T. falcatus, exhibits bone enlargement only in the ribs, while T. blochii only tends to get bone enlargement in certain cranial bones.

When you look at the historical accounts of T. anak “6 feet long” destroying oyster beds, even taking into account exaggeration by frustrated oyster farmers and loss of most of the benthic oyster beds along our east coast due to sedimentation from coastal development (thus reducing its food supply), it seems T. anak has a larger growth potential than T. blochii, potentially rivalling the size of the Atlantic permit such that it also rightly deserves the “Aussie permit” tag.

In the 1907 newspaper article and subsequent scientific descriptions of T. anak, much was made of the massively strong pharyngeal crushing plates in the throat, indicating a diet mainly consisting of molluscs and other hard shelled invertebrates such as crabs. Indeed, over the years the oyster cracker dart became infamous for occasionally being captured on pipis by bewildered surf fishers targeting dart and whiting. If you look closely at those old photos, I’m sure you can see their knuckles freshly skinned by the blurred handles of trusty Alvey reels…

Since the 1970s Trachinotus anak was considered rare and was seldom, if ever targeted by Aussie anglers (although it can be found along many of our sandy tropical beaches from Moreton Island in south east QLD right across the top end to around Shark Bay in WA). However, in the past decade or so they have become a relatively frequent capture for those sight fishing to tailing fish on our northern tropical sand flats, with both T. anak and T. blochii potentially being caught side by side in some locations, like Ningaloo Reef in WA.

Through hard work and a sense of exploration by a dedicated band of sport fishers and guides, the “where and when” behind the Aussie permit species is being demystified. The good news is the “why” remains unchanged. They remain as challenging as ever and the next person to go home empty handed after flycasting to an acre of schooling Aussie permit won’t be the first, or last.

THE BRISBANE COURIER, Thursday Nov 28, 1907, p 5.


By the steam of midday on Tuesday Mr R.W. Leftwich despatched to the Marine Department in Brisbane a fish which is claimed to have done considerable damage amongst the oyster beds in Hervey Bay (writes our Marlborough correspondent). The fish, it is said, made its first appearance in small numbers in 1886 but has latterly come in large shoals. After numerous attempts two specimens were caught on Saturday. They were about 3ft 6 in. long. The mouth contains no teeth but lower down are two sets of crushers by which the oysters are evidently smashed. The fish pick up the oysters while standing on their heads, as it were, with the tail near the surface, and are often 6 ft in length. One of the specimens caught was boiled, and inside were found quantities of broken oyster shells. Several instances of the ravages of the fish have been cited, and the owners of oyster beds have had to go to great expense in fencing in their culture banks with wire netting. In one instance where 28 bags of culture were laid out at noon on an unprotected bank it was estimated that at 10 o clock the following morning there were not 6 bags left. In other places where 1500 bags of culture had been laid out only 500 bags of oysters were reaped. The fish is an edible one and it was recognized by Captain Mackay, of the steamer Tay, as one known in the South Sea Islands, where it is termed “a shell eating fish”. Mr Leftwich considers that thousands of bags of oysters are destroyed yearly between Tin Can Bay and the Burrum River.

Mr J Douglas Ogilby, at the invitation of the Inspector of Fisheries, yesterday examined a specimen of this fish at the Port Office. After making a careful examination, generic and specific, he recognized it as a species which he had only known before in the young stage. The fish is ovate, with very small and elongated scales. The head is small in proportion to the bodv and the mouth small in proportion to the head. The snout is rounded and overhanging, and the jaws absolutely toothless. The spinous dorsal fin is reduced to a few short isolated spines. The front of the soft dorsal and anal fins are elongated. The caudal fin is deeply forked and shows great strength and power of propulsion. The breast fins are small and the ventral fins extraordinarily small. The colour is blue above and silvery everywhere else. Except for the snout, it resembles a trevally. In all recognised works 20 in. is given as the full size of this fish, but the specimen examined yesterday by Mr. Ogilby was 3ft. 8 in. It is purely pelagic – that is, lives in the open sea on the surface-and only comes in to shore for the purpose of spawning. The fish examine was a female, with the two ovaries fully extended, each ovary being about 8in. in length, and with a similar circumference. Apparently the ova were perfectly ripe and ready for extrusion, and each ovary, Mr Ogilby states, could not have contained less than 1,000,000 eggs, since each separate ovum was not larger than a pin’s head. Incidentally Mr. Ogilby mentions that in the case of pelagic fishes not more than one in 10,000 of the ova would come to maturity- hence this provision of Nature in furnishing the female fish with such a tremendous number of eggs.

The most important part of the economy of this fish is to be found in the means by which a toothless fish with a small mouth is destructive to oyster beds. A dissection of the head showed that the pharyngeal bones are enormously developed, are destitute of teeth, but form an ideal crushing apparatus. Owing to the smallness of the mouth these fishes are unable to pickup old and large oysters, and therefore confine their operations to the oysters newly laid down as culture by the lessees at great expense. Thus they are even more inimical to the interests of the lessees of the beds than the rays and toad fishes, which destroy the adult oysters bv prizing them off the substances to which they are attached, but which the fish under review is unable to do owing to the absence of teeth. The stomach of the specimen examined by Mr Ogilby was crammed with broken shells of young oysters, none of which would have exceeded 1 in. in diameter. The crushing apparatus referred to consists of two pairs of bones between the angles of the gills. The upper pair are separate, and can be moved by separate muscles. The lower pair are intimately connected, and lie opposite to the upper pair. When the oyster is taken into the mouth it is passed into the throat in a perfect state, but when it comes with the operation of these two pairs of bones they, working in opposite directions, at once crush the young oyster, leaving the mollusc and the crushed shell to be swallowed, and when the oyster itself is digested the broken shell is ejected through the mouth. None of the scientific works of reference credit this fish with mollusc-eating propensities, and it was never known to possess crushers; indeed all pelagic fishes practically confine their diet to fishes and squids. Mr Ogilby points out that it is very remarkable that this fish, which, as mentioned previously, lives on the surface in the open ocean, should when inshore develop the habit of bottom feeding and grubbing. This fish, which Mr Ogilby calls the “snubnosed swallow tail” is scientifically known as Trachinotus ovatus. It is an inhabitant of all tropical seas, no scientist having yet been able to note any material difference between the species of the Eastern and Western Hemispheres.


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