Thresher Shark – Updated
by Allan Burgess and Dick Marquand (see below)
The thresher shark is easily recognized from its very long tail. The upper tail lope is about the same length as the rest of the body. The upper body ranges from dark cobalt blue to a brownish grey. The belly and lower sides are white or light grey. The teeth are relatively small. There are five gill slits. They have smaller mouths and smoother skin than most sharks. The thresher shark’s diet consists of schooling fish, squid and pelagic crustaceans.
These sharks are quite slow breeding. They are ovoviviparous with the female giving live birth to just two to four young, each measuring about 1.2 to 1.4m. They reach sexual maturity at around 3m.
This shark uses its long tail as a whip to disable small prey species like pilchards, sprats and mackerel.
Threshers have been seen working alone, or in pairs, herding baitfish into tight schools by circling them before slashing through them with its tail, then quickly turning to consume any injured fish. Thresher sharks are also known to work in groups circling sprats and pilchards into a tight mass. As they do so they thrash the surface with their long tails.
Game fishermen trolling lures have also noted that threshers will strike the lure with their tails. This shark is able to select individual fish before striking them with incredible accuracy. The thresher, along with the great white and the porbeagle, is warm-blooded. Their blood is warmer than the surrounding water temperature. This makes it possible for them to achieve sudden bursts of great speed when pursuing prey.
The thresher is a powerful fighter for its size when taken on rod and line. It has also been known to jump clear of the water when attempting to throw the hook.
Threshers are recognized by the International Game Fish Association as a game fish. Many anglers consider the thresher shark more difficult to reel in than a mako of similar size. The preferred tackle is 24kg.
Most big game anglers take threshers either on deeply trolled lures (particularly with the aid of a downrigger) or on a drift bait.
Typically threshers will hit trolled baits or lures that have been set for marlin or tuna. The lures taken are often feathered jigs, Konaheads, Knuckleheads and the like. There are three different species of thresher shark but only one is found in New Zealand waters Alopias vulpinus.
They range all around the New Zealand coastline but are more common along the upper east coast of the North Island. Southern anglers catch thresher sharks off Fiordland and the Otago Peninsula. They are found worldwide in temperatures ranging between 16 to 24 C. The late David H. Graham in A Treasury of New Zealand Fishes describes thresher sharks caught off the Otago Heads that were up to eighteen feet in length. It should be noted that this was early last century. The largest he personally had examined was 9 feet six inches long. The threshers taken off Otago Heads were caught in from 5 to 80 fathoms.
Some very big threshers have been caught by members of the Tutuku Fishing Club in Dunedin. The New Zealand record thresher shark stands at 336kg. The average maximum length for a thresher shark is about 5m.
The stomach contents of thresher sharks examined by Graham were found crammed with pilchards, sprats, mackerel and red cod. Graham relates the frightening experiences of the commercial fisherman who have hooked thresher sharks on hand-lines set for groper at North Reef, off Otago Heads. The thresher would rush at the bait and then turn upwards for a short distance. At which point the line would suddenly slacken giving the fisherman the impression that the shark had got away. Then the hooked shark suddenly hurls itself up out of the water, and should it be near enough to reach the boat with its tail there is grave danger of damage to the craft as it descends.
They are generally regarded as a pelagic species but on occasion, they do come in very close to shore. I once saw a small thresher shark caught by a surfcaster fishing on Gentle Annie beach north of Westport on the South Island’s West Coast.
In years gone by threshers have also been caught by surfcasters fishing on Canterbury beaches south of Banks Peninsula. They are a rare catch for surfcasters or boat anglers nowadays. Special thanks to Ian Robertson for the above photographs.
Thresher shark with Dick Marquand
Other names: Thrasher, fox shark
Scientific name: Alopias vulpinus
Although there appears to be some confusion regarding how many species of thresher shark are found in New Zealand waters, I can confirm that all specimens of thresher shark I have seen caught off the South Island coastline are in fact the thresher shark (Alopias vulpinus).
This species has a solidly built body and is easily recognised by the elongated upper lobe of the caudal fin which is the same length as the body. The medium size eyes are located well forward in the head while the small mouth contains blade-like teeth. As to be expected, the caudal peduncle or wrist of the tail is thick.
Colouration on the upper surface can vary from a purplish grey, brown or black with metallic hues, while the undersides are a dirty white or cream. There is an aura of white over the bases of the pectoral fins
and often, a white tip of the pelvic fins and the lower lobe of the caudal ﬁn.
10deg. C to 22deg. C.
The thresher shark is cosmopolitan throughout tropical and temperate waters. During the summer and
autumn months, this species is regularly seen in all coastal waters of the South Island.
The International Game Fish Association (I.G.F.A.) groups all species of thresher shark under the
collective name Alopias spp.
The I.G.F.A. All-Tackle World Record is a 363.8kg (802lb) thresher taken on 37kg gear by Dianne North
fishing from Garth Marsland’s Maestro near the Poor Knights Islands on February 8, 1981. However, larger specimens have been taken in New Zealand waters. On 21 March 1937, a thresher weighing 418.22kg (922lb) was taken from the Bay of Islands by an English angler, W. W. Dowding, on 60kg gear. This shark eclipsed the record set by Stan Ellis on 12 March 1929 with his 415kg (915lb) thresher from Whangaroa waters. Both these records were removed from the books because the lines used in making the catches were not tested officially for their breaking strengths. At the time of writing, six New Zealand threshers are listed in the I.G.F.A. records, the largest from other than our waters being a 203.21kg (448lb) shark from Montauk, New York, U.S.A. taken on 24kg gear.
The thresher shark is a pelagic migratory species that hunt singly or in small groups for small schooling fish such as anchovies, sauries, pilchards, garfish, mackerel and kahawai.
After rounding up a school of small fish, this shark will use its long leathery tail with deadly efficiency to stun its prey. The thresher will often indicate its presence by flailing the surface or sending up small spouts of water.
Thresher sharks are usually caught while trolling coastal waters with lures or plugs, most notably Rapala plugs. Treble hooked plugs such as the Rapala CD 18 usually tail hook the shark when an attempt is made to “stun” the plug. If the plug is trolled very slowly, the thresher will generally take the plug in its mouth.
Threshers will also accept a drifted or trolled live bait such as a small kahawai or mackerel. Although I have seen this species taken in association with chum or berley I am not convinced that it was the chum that attracted the fish to the bait.
A light steel trace should be used to combat the effects of not only the small sharp teeth but also the fine abrasive skin when or if the shark rolls on the leader. For threshers up to 100kg (220lb), 15kg class tackle is ideal.
A thresher shark, especially if hooked in the tail, is a powerful hard fighting adversary and even a relatively small fish can take several hours to subdue. The initial run will completely spool reels that lack a reasonable line capacity. This species will on occasions leap clear of the water while being fought.
Care should be taken when dealing with the fish once it has been brought alongside the boat as it can use its tail with deadly efficiency, stunning a careless angler.
There appears to be some confusion with the thresher (Alopiidae family). There are their three or four species of thresher shark depending on whose information is sourced.
A Guide to the Sharks and Rays of Southern Africa by L. J. V. Compagno, D. A. Ebert and M. I. Smale, New Holland (Publishers) Ltd, London, 1989, lists three species – the smalltooth thresher (Alopias pelagicus), the thresher shark (Alopias vulpinus) and the bigeye thresher (Alopias superciliosus). This comprehensive publication shows the latter species ‘frequenting the eastern side of the southern African continent and lists it as being found in all temperate and tropical seas.
However, the I.G.F.A. publication 1993 World Record Game Fishes lists the three species already mentioned and a fourth, the Pacific bigeye thresher (Alopias profundus) which is found in the northwestern Pacific Ocean. This reference book lists the Atlantic bigeye thresher (Alopias superciliosus) as frequenting the Atlantic Ocean. To further confuse readers, Dianne North’s 363.8kg
(802lb) World Record thresher from Tutukaka waters is listed by the I.G.F.A. as being an Atlantic thresher (Alopias superciliosus).
“New Zealand Fish – A Complete Guide” by Chris Paulin Andrew Stewart, Clive Roberts and Peter McMillan, National Museum of New Zealand Miscellaneous Series No. 19, November 1989 lists only
one species of thresher shark (Alopias vulpinus) in New Zealand waters.
The reason for the confusion is obvious. I have requested that a New Zealand shark expert, Clinton Duffy, look into this matter.
The I.G.F.A. recognises thresher sharks in all line classes and saltwater ﬂy rod tippet categories for World Record Claims under the collective name of Shark, Thresher (Alopias spp.). The New Zealand Big Game Fishing Council also recognises thresher sharks as Alopias spp.
In Fiordland waters, I have often heard commercial fishermen mistakenly call sevengill sharks (Notorynchus cepedianus) thresher sharks.
The thresher shark is ovoviviparous; this means that the eggs hatch inside the uterus of the female and
obtain nutrients via a yolk stalk from a yolk sac. When at full term, four to six young are born, each weighing about 5kg (11lb).
This species is considered to be harmless to humans, although two attacks on boats have been reported.
More About Thresher Sharks by Dick Marquand
In the article above I explained the obvious confusion regarding the various species of the thresher shark. I have since spoken to Mr Clinton Duffy, the Department of Conservation’s expert on sharks, who is based in Napier. Clinton is also a member of the American Elasmobranch Society and is New Zealand’s representative on the International Shark Attack File (I.S.A.F.). From my discussions with him and the material he kindly supplied me, I can now confirm the following.
Fisheries biologists now agree on there being a single genus of thresher sharks, this being Alopias, and three living species, these being the thresher shark (Alopias vulpinus), the bigeye thresher (Alopias superciliosus) and the pelagic thresher (Alopias pelagicus).
Some years ago, it was believed that there were two species of bigeye thresher, the Atlantic bigeye (Alopias superciliosus) and the Pacific bigeye (Alopias profundus). It has since been recognised that these two are but one species, the bigeye thresher (Alopias superciliosus).
Of the three species of thresher found worldwide, two of these, the thresher shark (Alopias vulpinus) and the bigeye thresher (Alopias superciliosus) have been recorded from New Zealand waters. The third species, the pelagic thresher (Alopias pelagicus) has been recorded approximately 1600 kilometres north west of New Zealand.
As a quick identification guide, the thresher shark (Alopias vulpinus) has the dorsal fin set well forward so that the leading edge of this is directly above the rear edge of the pectoral ﬁns. However, it is the white area above the base of the pectorals which identifies this species.
The bigeye thresher (Alopias superciliosus) has a flat snout, huge eyes and a distinctive hump in the back, just behind the eyes. This species has large pectoral fins and the leading edge of the dorsal fin is set well behind a vertical line from the rear edge of the pectoral fins. The pelagic thresher (Alopias pelagicus) has eyes of a similar size to the thresher shark (Alopias vulpinus), however, the dorsal fin is set further back and there is no white patch above the bases of the pectoral ﬁns.
At present, thresher sharks are recognised as game fish by both the International Game Fish Association (I.G.F.A.) and the New Zealand Big Game Fishing Council (N.Z.B.G.F.C.) under the collective heading – Thresher Shark (Alopias spp.). However, this may well change in the near future.
The Southern Sportfishing Club has prepared and will be forwarding a submission to the N.Z.B.G.F.C. which will request this council to cease accepting thresher shark claims under the heading Thresher Shark (Alopias spp.) and instead accept these under Thresher Shark (Alopias vulpinus) and Bigeye Thresher (Alopias superciliosus).
The club feels that accepting claims and recording all thresher sharks collectively under the one heading does not do justice to the various species of thresher, nor does it do justice to the anglers, who because of this system, miss out on the opportunity of making a well-deserved record claim.
It is the club’s opinion that an angler catching a thresher shark (Alopias vulpinus) should not have to compete with another angler who catches a bigeye thresher (Alopias superciliosus) on the same line class of tackle.
The club’s committee believes that the acceptance of record claims‘ for threshers by the N.Z.B.G.F.C. should be subject to the inclusion of photographs with the claim to assist the council with the correct identification of the shark. The club also believes that photographs of existing thresher shark record claims could be used to determine the species so that current record holders are not affected.
If the Southern Sportfishing Club is successful with this submission, it intends approaching the I.G.F.A. and encouraging this organisation to alter its record keeping system for thresher sharks.
Special thanks to Rob Dinsdale, Records Officer of the N.Z.B.G.F.C. for forwarding the Northern Advocate photograph of Mrs Dianne North’s bigeye thresher.
Thresher Sharks Kill Prey with their tail. The thresher shark has one of the most dangerous tails in the ocean. It has evolved a deadly hunting tactic to kill its prey with its tail. Watch these thresher sharks in action.