Sevengill and Sixgill Sharks
by Allan Burgess
The Sevengiller and Other Cow Sharks
by Dick Marquand
In 1992 a large sixgill shark was taken in Cook Strait that measured 4.2 metres (14 ft) and weighed 417 kg (919 lbs)
There are three species of cow sharks found in New Zealand waters. These are the sharp-snouted sevengill shark (Heptanchias perlo), the broad-snouted sevengill shark (Notorynchus cepedianus), and the less common sixgill shark (Hexanchus griseus).
They are widely distributed throughout the world and can be found in temperate coastal waters around South Australia, Japan, Southern Africa, off South America, and the west coast of North America.
The cow sharks are easy to distinguish as they have only one dorsal fin set well back on the body unlike the two dorsal fins found on almost all other sharks. The sixgill and sevengill sharks also have a long upper lobe on their tail fins. Most other sharks, like the mako and blue shark, have five-gill slits.
As to colour, this seems to vary quite a bit. Some specimens of sevengiller I have seen are brown on the upper body with a scattering of small black and slightly larger white spots. Others have been more light grey in colour. The underside of the body is a whitish grey.
The sixgill shark is found in much deeper water and lacks the spots of the sevengill sharks. Indeed sixgillers have been found on the seabed of some of the world’s deepest oceans.
The sharp snouted sevengill appears to be less common, is more a deepwater species, has a larger eye, lacks the black spots, and is generally a bit smaller than the broad-snouted sevengiller.
The teeth in the sevengiller shark are narrow and hook-like in the upper jaw while those in the lower jaw closely resemble a serrated edge knife. The teeth in the lower jaw are extraordinarily sharp. Presumably, the upper teeth are for holding prey while the teeth in the lower jaw are for slicing and cutting.
The cow sharks are Ovoviviparous. The young develop from eggs inside the female and are born fully developed between 35 and 45 cm in length – probably one year after mating. Litters are large numbering somewhere between 66-102 pups.
Broad-snouted sevengill sharks inhabit shallow bays and coastal beaches. As such they are one of the few large sharks likely to be caught by surfcasters around the South Island. They respond well to berley (chum) released into the sea.
They seem to eat just about everything that comes their way. They will catch and eat live fishes including fast swimming kahawai and mackerel. They also feed on squid and octopus. I have caught quite a few sevengill sharks while surfcasting along Canterbury beaches over the past thirty years. On opening, their stomachs were found to contain an astonishing assortment of recent meals. These include a whole hare, a whole salmon weighing at least 12 lbs, the fins of a dolphin, red cod, and dogfish. They are also known to eat marine mammals including seals, other sharks and stingrays, together with a wide variety of bony fishes. Possibly some of these were washed out to sea by flooded rivers.
Some years ago members of the Canterbury Sport Fishing Club were fishing off Banks Peninsula when several large sevengillers were hooked in deep water. Before they could be hauled to the surface the hooked sharks were in turn set upon by other broad-snouted sevengill sharks. Presumably, a feeding frenzy quickly developed during which the other sevengill sharks congregated there had no hesitation in canalizing their mates! Sevengill sharks are not known to be dangerous to man but in such a situation I’m sure they would bite anything that moved! Sevengill sharks are also regularly caught while surfcasting from Canterbury beaches. See Sevengill Sharks from the Surf.
I have read reports that sevengill sharks off South Africa sometimes hunt cooperatively in packs to capture marine mammals including Cape Fur Seals and other species of large shark. This I find surprising! The sevengiller at first appears as a docile shark living out its life eating mostly carrion. However sevengillers are certainly capable of sudden bursts of speed. They are also capable of aggression towards other large sevengillers. Perhaps the most surprising thing of all, to me at least, is that sevengill sharks might have the speed to chase and capture fast swimming bony fishes such as kahawai. It is thought that broad-snouted sevengillers prefer to hunt in discoloured water which may explain how they can close in on prey before suddenly striking with a burst of speed.
Another interesting fact I read recently is that sevengill sharks are hunted for food by great white sharks.
Sevengill Shark Baits
Sevengill sharks will take almost any baited hook the angler might send their way. However, their skin is very much like course grade sandpaper and will quickly cut through monofilament line dragged across the body. Sevengillers, like all sharks, will roll as they attempt to escape capture. For this reason, it is best to use wire droppers on a Paternoster rig and make the backbone from very heavy mono to withstand this rolling.
In practice, you can sometimes be lucky in that a large sevengill can be landed from the beach without particularly heavy traces and leaders. It is important to keep your rod tip up and apply constant even pressure to bring the shark in. Sevengillers over about 6 feet in length are not good eating and are best released unharmed. I have also caught a big sevengill shark while fishing from the rocks at Taylors Mistake on the north side of Banks Peninsula. To see a big picture of the sevengiller I caught from Taylors Mistake on a 5/0 Gamakatsu octopus hook, and after it had been carried back to the truck.
There have been some very large cow sharks caught by New Zealand anglers over the years. Dick Marquand reports that in 1992 a large sixgill shark was taken in Cook Strait that measured 4.2 metres (14 ft) and weighed 417 kg (919 lbs). Many of the broad-snouted sevengillers caught by surfcasters weigh around 70 to 100 kgs.
Sevengill Shark Fossils
Fossil evidence shows that cow sharks have been around for some 200 million years. So perfect has been their design that nature has found no need to alter it. Perhaps the cow shark’s adaptability has been its secret of success. Indeed as we have seen with the broad-snouted sevengill shark there is more to this species than meets the eye. It can hunt as a pack for large prey, ambush smaller prey in shallow coastal waters, scavenge the carcasses of dead sea and land animals, find prey in turbid waters, and eat very little to sustain itself should the need arise.
The Sevengill and Other Cow Sharks
by Dick Marquand
The reel ratchet clicked as the line was slowly being drawn from the spool of the Penn International 30. I pinched the line between my forefinger and thumb and felt the steady increase of pressure on the line. “The waiting is over,” I said to Bill.
“I do believe that we are in business.”
It was about time too. For more than four hours, Bill and I had been anchored over the Transit Reef, chumming a sticky mixture of chopped up albacore, Jock Stewarts (sea perch) and tuna oil into the calm Fiordland sea. The long wait had been without incident and even the usual blue sharks had failed to ‘turn
up, but then, chumming operations are often like that. The bait was half a small albacore, set ten metres beneath a blue balloon which was now bobbing violently. The cotton line parted and the balloon, now freed from its restraint, drifted away from us in the light breeze.
I took the Fenwick 10kg game rod from the rod holder, disengaged the reel ratchet and applied light thumb pressure to the slowly revolving spool. Bill clambered around on to the bow and attached a pink ﬂuorescent buoy to the anchor rope and cast off so that we could drift away from the cray-pot ropes and the ﬂoats that dotted the reef.
“Is it a mako, a blue shark or a thresher?” I thought to myself.
“It’s now or never,” I said to Bill as I lifted the lever to the strike position. As the line came uptight, I wound in as much line as I could while striking hard in quick succession six or seven times. The carbon fibre rod bowed and the roller guides whirred as the fish ran in the direction of the mouth of Milford Sound.
“Do you want me to start the motor Dick?” asked Bill.
“Yeah O.K. Bill,” I replied, “but leave her out of gear.”
There were no exceptionally fast runs, just heavy steady pressure which left me wondering just what had taken the bait. Whatever it was, it was now about 150 metres from the boat and going strong.
Fifteen minutes into the fight, I felt that I was in command of the situation. By pumping the rod, I slowly gained line and eventually, the familiar “dirty line” wound onto the reel.
“Can you see it?” I yelled out to Bill who was perched high in the tuna tower. “It feels like a shark, but I can’t be sure. Perhaps you’d better get the ﬂying gaff ready, just in case.“
“I can see it Dick!” yelled Bill. “I don’t know what it is, but it looks big.
It was big, as the double line broke the surface and approached the rod tip, I could see the unmistakable brown shape of a shark in the clear blue water.
“It’s a sevengiller,” I said. “We don’t need to kill this shark Bill, so we’ll let it go.”
As Bill took the steel leader in gloved hands and eased it closer to the boat, I reduced the reel drag tension and placed the rod into the rod holder. It was indeed a broad-snouted sevengill shark and with an estimated length of nearly three metres, it was by far the biggest of the species that I had ever seen. The sharp 9/0 forged game hook could be seen – ﬁrmly embedded in the corner of its mouth, but one look at the ferocious teeth and I decided that discretion dictated that the hook could stay there. I slid the side cutters down to the eye of the hook and snipped through the steel leader. The blunt head with its expressionless eyes slipped back into the water and the shark swam out of sight, down towards the seabed.
The broad-snouted sevengill shark (Notorynchus cepedianus) has a worldwide distribution but to my knowledge has not yet been recorded from the Mediterranean Sea or the North Atlantic Ocean. It is often encountered by anglers who fish around the coastline of the South Island of New Zealand.
This species is one of three members of the cow shark family (Hexanchidae) found in New Zealand waters, the others being the perlon shark or sharp snouted sevengill shark (Heptanchias perlo) and the sixgill shark (Hexanchus griseus).
The broad-snouted sevengill can be identified from other cow sharks by its seven pairs of gill slits, small eyes and a blunt broad snout. It is also known in some parts of the world as the broad-headed sevengill shark. In our southern waters, I have heard some commercial fishermen incorrectly refer to
this species as a thresher shark.
The broad-snouted sevengill shark, like all cow sharks, has only one dorsal fin instead of the two dorsals that are found on all other sharks apart from the closely related frill shark. This single dorsal is located well towards the back of the body. The tail fin has a long upper lobe.
The colouration on the upper surface is brown with a sparse scattering of black and white spots, while the underside is creamy white. The teeth in the front of the upper jaw are fang-like while those in the lower jaw are razor sharp and comb-like.
Although regarded by some as potentially dangerous to man, the only attack, if you could call it an attack, that I have heard of is an aquarium worker being bitten on the ankle by a sevengill shark. The species can grow up to a length of around three metres.
Groups of broad-snouted sevengill sharks have been reported in the vicinity of Open Bay Islands off the coast of South Westland, often swimming in a lazy manner just below the surface of the sea. I do not know the reason for this, perhaps they are grouped together for breeding purposes, or maybe it is
the colony of southern fur seals on the islands that hold their interest.
Little is known about the reproduction of this species, but like other cow sharks, the broad-snouted sevengill shark is thought to be ovoviviparous, that is the young develop inside the body of the female and gain nourishment from a yolk sac by way of a yolk stalk which is attached to the embryo. Litters are
probably large as one female was found to be carrying 83 large eggs. The smallest free-swimming specimen recorded is 53 centimetres (21 inches).
In the South Island, the broad-snouted sevengill shark is targeted by anglers involved in fishing competitions and also by some surf anglers.
The broad-snouted sevengill sharks that I have caught have mostly been taken from boats in the vicinity of reefs and foul ground. However, I do know of some that have been caught off sandy beaches and others from harbours, notably in the Otago Harbour.
The species appears to be an opportunistic feeder and specimens have been found with pilchards, mackerel, kahawai, small sharks, squid, octopus and crabs in their stomachs. I have caught them on cut baits and drifted dead fish baits, most cases in conjunction with extensive chum trails. The impressive teeth of this cow shark are evidence that a steel trace is essential. Although the broad-snouted sevengill shark lacks the power of the mackerel sharks, whalers and threshers, it nevertheless puts up a determined fight, especially on light game tackle or surf casting gear.
The only other cow shark with seven pairs of gills is the sharp-snouted sevengill shark or as it is also known, the perlon shark. This species has a sharp narrow snout, a slim body and larger eyes than its broad snouted cousin. Colouration is brownish grey with pale undersides and the tips of the dorsal and
tail ﬁns are black.
The sharp snouted sevengill shark is generally a deepwater species that frequents the continental slope, however, it has also been caught in waters of only moderate depth. This shark grows to a length of nearly two metres and is unlikely to be encountered by anglers.
Of two known species of sixgill shark, only one has so far been found in New Zealand waters, this being Hexanchus griseus. This deepwater species is found worldwide in temperate and tropical waters and has been recorded in depths of up to 1800 metres (5900 feet).
The teeth are similar to those of the broad-snouted sevengill shark. Colouration is generally a dark grey or brown with whitish undersides. The head is blunt and as with other cow sharks, the single dorsal finis set well back.
The sixgill shark is known to grow to a length of five metres (16.5ft) and can weigh up to 600kg (1320lb). It is known to feed on crustaceans and fish, including small broadbill swordfish and marlin.
My only encounter with this rare species was in January 1979 at the mouth of Milford Sound. While hauling up a groper line from 60 fathoms, an unusual shark came to the boat. It was a brownish grey in colour and lacked the spots displayed by the broad-snouted sevengill shark. The six pairs of gill slits immediately identified it as the sixgill shark (Hexanchus griseus), an identification which was later verified by photographs that I sent to Professor A. F. Garrick of Victoria University. Although usually a deepwater species, our specimen had come from relatively shallow waters and was the first sixgill shark to be recorded from Fiordland. It was a relatively small specimen weighing only 32kg (72lb).
A much larger sixgill shark was taken in Fiordland waters in April the following year by commercial fisherman Ron McDuff, keeper of the Blanket Bay Hotel on Secretary Island. Don caught the shark on a groper line and as it surfaced, he dispatched it with a shot from his trusty Lee Enﬁeld .303. When
some enthusiastic members of a Fiordland Game Fishing Club expedition spotted the shark at Blanket Bay, they decided to tow it back to the Club’s camp in Deas Cove and spin a wild yarn. The truth eventually came out and next day the shark was hung on a tree for some posed photographs. One of the Club members, Geoff Jukes, said that the sixgill measured around 3.6 metres in length and weighed an estimated 370kg (800lb).
In August 1992, another large sixgill shark was taken by Nelson Sealord’s staff while trawling for hoki in Cook Strait. This specimen measured 4.2 metres (l4ft) and weighed 417kg (919lb).
I would encourage any angler who catches a sixgill shark (or any other unusual shark for that matter) to carefully record its fork length, girth, weight (if possible), sex, reproductive state (if female), stomach contents, date, location, method taken, estimated depth of water and send this information and clear photographs to the Department of Conservation’s shark expert Clinton Duffy, D.o.C., P.O. Box 644, Napier. Clinton tells me that if possible, a section of the vertebral column taken from forward of the dorsal fin would also be both very helpful and most appreciated. This information along with photographs and samples will help us to gain more knowledge about the sharks that frequent our coastline.
The cow sharks are one of the oldest families of sharks that are still surviving, having appeared in the oceans about 200 million years ago. I have picked up their fossil teeth in a number of places in New Zealand, most noticeably in the limestone country of the Kakanui area.
When next you bring a broad-snouted sevengill shark alongside your boat or to the edge of the surf, take a few seconds to wonder at this unique creature before you use the gaff. Cow sharks are so close to perfection that even nature has had little reason to make”evolutionary changes to this
family or to cause it to become extinct. Obviously, these sharks have lived in harmony with the oceans of the world for a lengthy period of geological time. In comparison, man has been on this planet for but a blink. Perhaps we can learn something from this lesson in survival.
Sevengill shark caught surfcasting at the Rangitata River mouth.
Sevengill shark caught at Black Rock, Banks Peninsula.
Sevengill shark caught surfcasting at Birdlings Flat.