New Zealand Sea Fishes

Thresher Shark – Alopias vulpinus – easily recognized from its very long tail

Thresher Shark – Updated

by Allan Burgess and Dick Marquand

Table of Contents


The thresher shark is easily recognized for 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.

Thresher shark caught off Fiordland. Photo courtesy of Dick Marquand.

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 their 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 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 sharks 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.

Thresher shark caught surfcasting at Birdlings Flat, Canterbury. Photograph, Ian Robertson

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.

Thresher shark caught surfcasting at Birdlings Flat, Canterbury. Photograph, Ian Robertson.

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.

This thresher shark was caught on the morning of 20 December 2010 at Birdlings Flat south of Banks Peninsula by Ian Robertson. The estimated weight of the big shark was over 60kg. It was taken on 35 lb braid spooled on a Tica reel and 4.5 m telescopic surf rod with a prawn, squid and mussel combination bait. There may have been a small fish on the line before he struck. The battle lasted over an hour. Ian was fishing for elephant fish at the time. Well done Ian!

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

Identifying Characteristics:

Although there appears to be some confusion regarding how many species of thresher sharks are found in New Zealand waters, I can confirm that all specimens of thresher sharks 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 smallmouth contains blade-like teeth. As to be expected, the caudal peduncle or wrist of the tail is thick.

The 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.

Temperature Range:

10deg. C to 22deg. C.

Distribution:

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.

Size:

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, the U.S.A. taken on 24kg gear.

Habits:

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.

The white area immediately above the base of the pectoral fin and the forward position of the dorsal fin identifies this 68.95 kg (152 lb) shark as a thresher shark (Alopias vulpinus). Ian Aitken
made this capture near Milford Sound during February 1980. 

Fishing Methods:

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 Rapala 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.

Fighting Characteristics:

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.

General:

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.

The view of Ian Aitken’s thresher shows the powerful build of Alopias Vulpinus.

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).

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The flat snout, huge eyes and the hump in the back immediately behind the eyes identify this shark as a bigeye thresher (Alopias superciliosus). The shark weighed 363.80 kg (802 lb) and is the current l.G.F.A. All Tackle World Record. The smiling lady angler is Mrs Dianne North and holding the thresher’s tail is Garth Marsland, skipper of the successful game boat “Maestro.”
Photo by courtesy of the Northern Advocate.

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.

Video: Thresher Shark Hunting

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.

Catch a Threasher by the Tail

By Dick Marquand

The thresher shark closed in on the “meatball” of anchovies. She had been herding the school together for several minutes, setting them up for an attack. The sunlight that filtered through the sea’s surface flashed in unison on the hundred silvery sides as the school darted about frantically. For the tightly packed school of anchovies, there could be no escape. The shark swam directly into the school, her long tail lashing out with deadly accuracy. The anchovies scattered in panic, but not before she had launched her second attack. Broken bodies of a dozen anchovies hung suspended in death. The thresher turned and swam back towards the dead anchovies, methodically consuming them. Seconds later, all that remained was the flicker of scales reflecting sunlight on the disturbed water. How to catch a thresher by the tail.

Vibrations – Thresher by the tail

The shark became conscious of a constant vibration close by and she turned towards its source. Behind an area of disturbed water, she saw a brightly flashing fish, and from its vibrations, she sensed that it was wounded. Her feeding instincts were aroused as she swam after the fish.

She lashed out with her tail and felt contact, then turned to consume her prey. As she did, she became aware of a slight drag on her tail. She panicked and swam away, conscious that something was wrong.

Onboard the game fishing launch, the excited angler grabbed his rod from the rod holder as 10kg line was stripped from his screaming reel. “It’s a good one! I saw its tail hit the lure!”

Thresher shark is the name given to four separate species of the genus Alopias, and of these, at least two are found in New Zealand’s waters. The most common is the fox thresher, Alopias vulpinus.

The  International Game Fish Association (I.G.F.A.) which is the body responsible for the keeping of world records, recognises the difficulty in correctly identifying the various species and has collectively grouped them together under the name – Shark, thresher/ Alopias spp. Of the 17 l.G.F.A. line class records, six have gone to anglers fishing New Zealand’s Bay of Islands, Tutukaka and Mayor Island waters. The All Tackle Record 363.8Okg (802 lb) thresher was taken on 37kg gear by Dianne North fishing from Garth Marsland’s “MAESTRO” at Tutukaka in 1981. However larger specimens have been taken in New Zealand, one weighing 418.22kg (922 lb) was taken from the Bay of Islands and another of 415.04 kg (915 lb) came from Whangaroa waters.

The largest thresher in the record books taken outside New Zealand is a 203.21 kg (448 lb) shark from Montauk, New York in 1984. It is therefore obvious that New Zealand is also famous in gamefishing circles for its large threshers.

During the summer and autumn months, the fox thresher is found throughout the South Island’s coastal waters. I have reports from the Marlborough Sounds (remember the video “Bill Hohepa Goes Fishing), Kaikoura, Banks Peninsula, Otago Heads, Tautuku, Foveaux Strait, Fiordland, Jackson Bay and Greymouth.

The thresher has, in relation to its body, a small mouth and feeds on small schooling fish. The smaller sharks up to about four metres long (counting the tail which is the same length as the body) feed on anchovies, garfish, pilchards and small mackerel.

Larger threshers feed on kahawai, mackerel and other species of schooling fish. They hunt either singly or in small groups, rounding up fish into a tight group referred to by gamefish anglers as a “meatball”. The thresher will then swim through the school, its tail lashing out with deadly accuracy, incapacitating its prey.

My personal experiences with thresher sharks, apart from one incident with a “monster” at Mayor Island, have been restricted to Fiordland waters, mainly in the vicinity of Milford Sound. All apart from one taken on a live kahawai by Sir William Stevenson were taken on trolled lures.

From experience, the most deadly lure for threshers is the Rapala CD 18 plug, and the preferred colour appears to be fluorescent red – what baitfish this colour represents I have no idea. The CD 18 is deadly because of the following features. The vibration from this plug imitates a wounded fish. The shiny metal bib acts as a paravane taking the lure below the surface and emits flashes of reflected light which I am sure helped to attract predators such as the thresher. The lure is equipped with two The mackerel Pattern CD 18 and the black and silver CD 18 work well on threshers, but the fluoresent red model is the most productive. The sets of deadly treble hooks seem to have an affinity for thresher tails.

I have seen threshers taken on hex heads and konas, but in all honesty, the hookup success rate is nothing like what you can expect when trolling the CD 18. I have watched these sharks come up behind the boat, past fancy konas and other lures, to “home in” on the CD 18 plugs.

The CD 18 is an excellent lure for trolling on 6 kg, 8 kg, and 10 kg outfits, but is marginal on 15 kg gear. When using the latter I.G.F.A. line class, heavy pressure on a Rapala CD 18 plug, which is firmly fixed in a thresher’s tail, can cause the treble hooks to straighten out and result in a lost fish. l have seen a few threshers landed on Rapala plugs trolled from 24 kg gear, it can be done providing the drag tension is kept really light and the skilful skipper keeps close to the hooked shark. I have known some anglers who have fitted heavier treble hooks but in my experience, this tends to spoil the balance of the lure.

The “hot months” for South Island’s threshers are from January to May, peaking in February and March. The hottest location that I have seen for this species is Milford Sound and everything inside a line from the south end of Transit Beach, to Brig Rock, then to Yates Point. However, as I have mentioned previously, they feed on schooling fish, so keep an eye out for seabirds working inshore, particularly white-fronted terns.

Sometimes, when a group of threshers are working a school of baitfish, you may see the top of the caudal fin flailing the surface, or you may see spouts of water erupting up to a metre from the surface of the sea.

Threshers, like marlin and tuna, do not appear to be boat shy and l have on many occasions seen them lashing out at Rapala CD 18 plugs trolled only five metres from our stern. Rapalas are expensive and I always troll them on light steel traces without a swivel, to avoid a “cut off” from barracouta.

The plug wobbles as it swims and if running correctly, the rod tip vibrates constantly. If you troll your plug at less than three knots, the thresher is likely to take the lure in its mouth. The reel drag should be set as lightly as possible, on tight drags I have seen threshers belt the lures so hard that the line has broken.

Watch the wake

To get the best out of thresher fishing, it pays to have someone watching the wake. When you see water spouts erupting close to your lures, you are close to being in business. If the thresher hits the lure and doesn’t hook up, be patient and do not alter your engine speed, the chances are that he’ll be back.

Shark strikes!

When the shark strikes, the initial run will be long and strong, taking out perhaps a couple of hundred metres of line. lt goes without saying that your reel must have a smooth drag and if your spool gets down on line, ease off the drag. Fighting a thresher hooked in the tail is an exciting experience and if you and your skipper operate as a team, in perhaps two or three hours, you will get your first glimpse of a truly wonderful and highly adapted fish.

Whoever takes the steel leader must be aware that the shark may only just be hooked, so it is not a matter of hauling on the wire. Be gentle and if the fish wants to go, let the leader go. I lost a certain New Zealand Record and possibly a World Record thresher on 10kg gear all because the “wireman” hauled too hard on the leader and straightened the hook. lt had taken me two hours and 55 minutes to bring the fish alongside my boat.

By the tail first – A thresher by the tail

Another important point is to remember that the shark will probably be coming up tail first and you may have to take the tail and lift the fish so that it can be gaffed or tagged.

I can vividly remember trying to hold a “green” fox thresher by the tail as it went berserk. The sight of a fluorescent red CD 18 with deadly treble hooks going backwards and forwards past my face was too much for me and I was forced to let go. The plug flew free and the shark regained its freedom.

Another friend, Dr Pat Farry was nearly concussed by a New Zealand Record thresher that he took on 10 kg gear back in 1978. He had done his bit fighting the fish and as he leaned over the side to view his prize, a long leathery tail lashed out and belted him in the side of the head. The king hit sent him reeling across the cockpit.

One of the most exciting sights that I have witnessed is a thresher shark right in behind the boat lashing out at my lure.

Around the South Island coast, there is some exciting sport waiting for the dedicated and persistent angler. You may have to troll your lures for a great distance, but when you finally connect, you will have your chance to catch a thresher by the tail. Here is another article on the thresher shark by the same author Dick Marquand.

Dr Pat Farry with the first thresher taken by a member of the Fiordland Gama Fishing Club.

This post was last modified on 15/09/2021 6:50 pm

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