Richard Robinson Living World Speed Demon Built for acceleration and power, the shortfin mako is the fastest shark in the world and an icon of New Zealand seas. Although heavily fished for decades by commercial longliners, mako populations are beginning to recover, and prospects look good for this oceanic speedster.

Written by Kennedy Warne Photographed by Richard Robinson

A cream-white torrent of water burst nearer to us, and out of it whirled the mako going up sidewise, then rolling, so his whole under side, white as snow, with the immense pectoral fins black against the horizon, shone clearly to my distended eyes. His terrific vigor, his astounding ability, were absolutely new in my experience with fish. Down he smashed into a green swell. We all heard the crash.”

It was rip-snorting prose like this, by celebrity angler Zane Grey in his 1926 classic, Tales of the Angler’s Eldorado, New Zealand, that brought the bullet-headed rocket-fish known as mako into the minds and imagi­nations of readers around the world.

Yet google “mako” and dominant among the 34 million results you get are not refer­ences to an iconic species of shark, but a cybersecurity company, a web template, a Japanese voice actor, a dance-music duo, a rentable bach on Waiheke Island and a sans-serif font. Only halfway down the second page of results is an entry from Te Ara Encyclopedia of New Zealand which begins: “Short-finned mako are the fastest of all the sharks. Muscular and powerful with a stiff body, they weigh up to half a tonne. They have long, curved teeth and feed on . . .” You have to click to find out.

“Mako”, in fact, may be one of the most widely appropriated Maori words in the world. It is a word with deep etymological roots in the Pacific, sharing an ancestry with mago in Samoan, ma’o in Tahitian and mano in Hawaiian. Pau pele, pau mano—“consumed by volcanic fire, consumed by shark”—was used as an oath by Hawaiians, implying, “May I die a grisly death if I fail to keep my pledge.”

In Maori, the generic word for shark is mangō, while mako refers specifically to the mako species, but also to an individual mako tooth. Mako teeth were highly valued for necklaces, ear pendants and cutting tools. Missionary William Colenso wrote: “I invari­ably found that all the teeth I saw were prized heirlooms, and had descended to the present possessor through several generations.”

One of Colenso’s informants told him that mako sharks were not taken by Maori for food, but only for their teeth. Moreover, they were caught by lassoing the tail. When that happened, “away would speed the canoe at a fleet rate towards all sides of the sea and sky”, Colenso’s source told him. Once the shark was exhausted, it was killed and the head cut off for later tooth extraction. From this practice of noosing a mako the term “monster-binding”, here taniwha, arose.

There are two species of mako: shortfin and longfin. The longfin, so named for its outsize pectorals, is more slightly built and much less common than the shortfin, and is not found in New Zealand waters.

The shortfin mako’s scientific name, Isurus oxyrinchus, was bestowed in 1809 by Constantine Rafinesque, an eccentric polymath from the Ottoman Empire who named no fewer than 6700 species of plant during his life. The name displays a classical approach to taxonomy: identify a couple of diagnostic features of the organism, trans­late into Greek—job done.

Isurus means “equal tail” while oxyrin­chus means “pointy nose”. The latter is accu­rate—no shark has a more conical snout than the shortfin mako, as if the animal had had an encounter with a pencil sharpener. “Equal tail” isn’t quite right, however. The upper lobe of the caudal fin is slightly longer than the lower, though this detracts little from the appearance of a crescent of raw power that propels the animal through the sea at speeds said to reach 70 kilometres per hour on the burst.

This impressive velocity is achieved, in part, by the mako’s high metabolic rate, which arises from (and is fuelled by) an ele­vated body temperature. Like other members of the group known as lamnid or mackerel sharks—great white shark, salmon shark, porbeagle—mako sharks can maintain parts of their body at up to 14ºC higher than water temperature .

This phenomenon, known as endothermy, has a metabolic cost, but also some distinct benefits. Because lamnid sharks maintain a constant elevated temperature in their stom­achs, their digestive enzymes can work much more rapidly than is the case in ectothermic fishes. Swift food processing makes energy quickly available to muscle tissues—a meta­bolic asset that enables mako sharks to spend extended periods in water as cold as 5ºC without suffering a slow-down in activity. Ectothermic sharks, by contrast, must return to warm water in order to digest their prey efficiently and recharge their muscles.

Another factor in mako speed is the skin’s low coefficient of drag. Shark skin famously inspired the full-body swimsuits used by Olympic swimmers Ian Thorpe and Michael Phelps, but the fabrics in those suits were pale imitations of the complex dermis of a real shark.

In 2012, Harvard ichthyologist George Lauder used a micro CT scanner, a 3D printer and some sophisticated computer modelling software to replicate mako skin in artificial form. His team’s major challenge was com­bining both hard and soft structures within a single material. A critical component in shark skin are millions of tiny “teeth” called denticles. It is these that give shark skin its sandpapery texture. Shaped like three-pointed adzes, mako denticles protrude above and curve over the underlying softer skin tissue. They are structurally similar to mammalian teeth: a core of dentine covered with enamel.

When Lauder debuted his material, he claimed that it both reduced drag and increased thrust. “The denticles create a low-pressure zone, called a leading-edge vortex, as the water moves over the skin,” he said. “You can imagine this low-pressure area as sucking you forward.”

Because the denticles are shaped differ­ently on different parts of a shark’s body, Lauder speculated that they might serve differing roles. “If you watch a shark swim, the head does not move very much, so it could be that the denticles on the head are mostly reducing drag, but those on the tail are enhancing thrust,” he said in a report in the Harvard Gazette.

As well as potentially providing swim­mers with more speed for less energy expenditure, the material being worked on by Lauder and his co-workers may have appli­cations in marine anti-fouling, perhaps replacing toxic paint coatings with environ­mentally friendly sharkskin surfaces that achieve the same result.

Adding denticles to aircraft surfaces could potentially reduce drag, though whether the savings in fuel would outweigh the cost of the coating is hard to say. Essentially, any surface over which air or liquid flows, and where drag is a problem, may benefit from sharkskin technology: rudders, fans, wind turbines, rockets.

Such biomimicry—human engineering solutions that emulate patterns and pro­cesses in other living creatures—is a bur­geoning field of research and development. But in one famous case, involving a sports car, it worked in reverse.

Bill Mitchell, a senior executive at General Motors, had been on a fishing trip to Bimini in the Bahamas, and returned with a mako, which he had stuffed and mounted to hang on his office wall.

“I kept looking at it on the wall, and I said, ‘I’m going to make a car that looks like that’,” Mitchell recalled in an interview after he retired. When you’re vice-president of styling in one of the world’s largest car companies during the prosperous, car-mad ’60s, you get to follow through on a whim like that.

Mitchell commissioned one of his top designers, Larry Shinoda, to develop a version of the Corvette Stingray that incorporated shark-like features derived from the fish hanging on his wall. According to Mitchell, his instructions were: “Take the Stingray design and keep doing it until I say, ‘Ouch!’”

Shinoda’s design included features such as side exhaust pipes that mimic a mako’s gill slits, front indicator lights concealed behind similar slit-like flaps, a bodaciously elongated bonnet and, most mako-ish of all, a graduated paint job that replicated the shark’s own hues—from a blue-black dorsal to a grey-white belly.

But try as it might, the paint shop couldn’t get the colours right. Mitchell kept sending it back for a respray. Frustrated by their ina­bility to match car to fish, the painters sneaked the trophy off Mitchell’s wall and repainted the fish to match the car, before returning it to the boss’s office. Mitchell, none the wiser, congratulated them on their skill. “You guys really captured it!” he said.

Though sleek and fast as the shark that inspired it, the Corvette Mako Shark never went into production. It remains a delicious footnote to motoring history and a tribute to one of the sea’s most beautifully propor­tioned creatures.

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Mako sharks are loners. Unlike great whites, which form aggregations at sites of high prey density (such as seal colonies), mako appear to be solitary predators, capable of very long migrations. One Australian mako was caught and fitted with a satellite tag in the Great Australian Bight, and subsequently crossed the Indian Ocean almost to South Africa, a journey of 25,550 kilometres.

There are significant patterns in age and distribution of mako sharks around New Zealand. Adult females are rare—only one pregnant female has ever been recorded in our waters—but males of all ages are to be found around New Zealand. Juveniles are most abundant in warmer, northern waters—and there are plenty of them. NIWA senior shark scientist Malcolm Francis says we have what amounts to a nursery popula­tion of mako sharks—but no one knows where the females give birth. “We see lots of babies, so they can’t be born too far away,” he tells me when I meet him prior to the annual Marine Sciences Society conference in Auckland. “We haven’t been able to tag any adult females yet, to see where they migrate to. That’s on the wish list.”

Despite their widespread distribution—around New Zealand and the world—short­fin mako are not often resident in waters cooler than 15ºC, and they are more common in the north of New Zealand than further south. They eat mostly schooling fish such as mackerel and tuna, but overseas research­ers have found the remains of dolphins and pinnipeds such as juvenile sea lions in their stomachs. “They’ll probably have a go at anything,” says Francis, including deepwater species such as swordfish and squid. “Sharks, with their excellent electro­magnetic sense, can probably detect them in the dark depths.”

Males and females grow rapidly until between seven and nine years, after which the relative growth of males declines. Males are sexually mature at around nine years old, and reach maximum lengths of about three metres. Females, which do not reach maturity until 19 or 20, can grow to at least four metres. Both males and females do not live beyond about 30 years.

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Age at maturity is a critical factor influ­encing the productivity of a species, which determines its ability to rebound from harvest pressures and maintain healthy numbers over time. With the late maturing of females (in human terms, the equivalent of a woman starting to bear children at age 46), populations of shortfin mako sharks are vulnerable if they drop to low levels. For sharks, the greatest mortality comes from fishing pressure—pressure that has tradi­tionally come from both the recreational and commercial sectors.

Mako have long been seen as a prime game-fishing target. Here is one of the many mako hook-ups described by Zane Grey, the American dentist-turned-pulp-Western-writer who was captivated by New Zealand’s swordfish, marlin and sharks:

“The mako turned over, cut the water like a knife and went out of sight; then leaped again, this time still more wonderfully. Down he went, slick, like a champion diver. Up again, high—fully thirty feet! I shouted in my excitement. He turned clear over in the air, and slid down into the sea.”

The taking of mako by recreational anglers continues to this day, but an estimated three-quarters of those caught are tagged and released. And as Francis tells me, mako mor­tality from recreational fishing is negligible compared with that from tuna longlining.

Mako sharks had little protection from commercial fishing pres­sure until 2004, when they—along with blue sharks and porbeagles, the other two species that are commonly caught on tuna longlines in New Zealand waters—were brought into the Quota Management System. Pre-QMS, fishers could retain or discard any number of these sharks at their discretion. Post-QMS, they have to own quota in order to land them, and regulations governing the discarding of dead sharks have been tightened. Live and dead animals may be discarded at sea, but they must be recorded, and dead discards are tallied against a fisher’s annual catch entitlement.

The annual Total Allowable Commercial Catch of mako is currently set at 200 tonnes. In the past seven years, the landed weight of mako has fluctuated around 100 tonnes, but it dropped to half that in 2014, despite more sharks being caught that year. The majority were discarded alive.

Mako bycatch has been declining on the back of a reduction in fishing effort in the tuna longline fishery. “Fishing effort has plummeted in the past 30 years,” says Francis. In the early 1980s, when many Japanese vessels fished our waters, longliners were setting 25 million hooks a year. By 2013, that number had dropped to 2.7 million. In 2014, there were only 37 domestically owned and foreign-chartered longline vessels operating here, down from 151 in 2002.

A reduction in bycatch may be also attrib­uted to mitigation methods adopted by fishers, including the use of nylon leaders (which sharks can bite through), larger hooks (which may make a bait less available to juve­nile sharks) and squid bait (less attractive than fish bait).

The rising percentage of live discards of mako by longline fishers may be a response to new regulations governing shark finning which were introduced in October 2014. Although it has always been illegal in New Zealand to fin a live shark—a brutal practice whose exposure elsewhere has helped gal­vanise public opposition to shark finning—the new regulations made it illegal for a commercial fisher to remove the fins from a dead shark and discard its body at sea. Now if fishers want to land shark fins for sale they must also land the trunks of the animals they came from. Given limited hold space on fishing vessels, the economics probably don’t stack up.

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In a further move to help to stem the decline in shark numbers worldwide, in July of this year the New Zealand government signed an international agreement to con­serve seven species of migratory shark: both types of mako, basking sharks, great whites, porbeagles, whale sharks and spiny dogfish. All are vulnerable species that have been depleted by a combination of accidental flesh, and all display the combination of life-history features that has led to the decline and extinction of many of New Zealand’s terrestrial species: slow growth, late matu­rity and the production of few offspring.

The evidence from New Zealand fisher­ies is that for species under most pressure, including mako, numbers have stabilised and may be increasing.

For those who admire the rocket of the sea, this is very good news.

Does a Mako feel cold? Almost all fish are “cold-blooded”, or ectothermic. Their body temperature is close to that of their aquatic habitat. There are, however, a few exceptions. Some tunas, billfishes and moonfishes, along with all lamnid sharks—mako, white, porbeagle and salmon shark—can maintain many of their organs and tissues at temperatures between 4ºC and 14ºC higher than ambient. These fish have elaborate meshes of blood vessels known as retia mirabilia (“wonderful nets”), which act as heat exchangers, enabling metabolic heat generated by the gut during digestion to be retained in the surrounding tissues rather than being lost to the environment as the blood passes through the gills to be oxygenated. As a result, these fishes—all of them predators that swim continuously over large distances of ocean and dive repeatedly from warm surface waters to cooler depths in pursuit of prey—are thought to be able to digest and assimilate their food more rapidly than ectotherms can, fuelling a higher level of metabolic activity. Scientists researching endothermy in lamnid sharks found that the enzyme trypsin was 27 times more active in a mako shark, which maintains a stable visceral temperature of approximately 25ºC, than in a thresher shark, a closely related species whose internal body temperature is around 15ºC. The researchers theorise that stable temperatures in the guts of lamnid sharks have allowed them to expand their activities into deeper water and higher latitudes, because they are physiologically buffered against a drop in ambient water temperatures. In addition, the excess nutrients accruing from a higher metabolic rate are thought to be stored as lipid reserves—to be drawn on during long migrations—and yolk for pups. The heat generated in the retia mirabilia is used strategically; not all organs are heated to the same level. So while propulsion muscles and digestive organs are maintained at a high operating temperature, blood circulation is not. Mako may have warm stomachs, but they have cold hearts. + Read sidebar