Raggedtooth shark

People find it hard to believe that a shark they can reliably dive with on Aliwal Shoal is Critically Endangered. The reproduction explains it completely.

THE SPECIES HAS TWO UTERI AND PRODUCES TWO PUPS. Not two per uterus — two in total.

THE REASON IS INTRAUTERINE CANNIBALISM. Several embryos start in each uterus. The largest one eats the others, then continues to feed on unfertilised eggs the mother keeps producing. What emerges is a single very large, very well-developed pup per uterus, ready to hunt.

GESTATION IS NINE TO TWELVE MONTHS AND FEMALES BREED ROUGHLY EVERY SECOND YEAR. So the maximum output of a mature female is about one pup per year, across a life that starts breeding late.

COMPARE THAT WITH ALMOST ANYTHING ELSE THAT SWIMS. A galjoen is a batch spawner releasing many thousands of eggs across a five-month season. A skipjack tuna spawns opportunistically all year. A raggedtooth produces two young and then waits two years.

WHICH MEANS THE POPULATION CANNOT ABSORB ADULT MORTALITY OF ANY KIND. Fishing, netting, bycatch, bather-protection nets, a shark killed by a bad release — each of those removes an animal that would have produced perhaps one pup a year, and no amount of good habitat replaces it faster.

AND IT IS WHY BEING COMMONLY SEEN PROVES NOTHING. The aggregations that divers visit are the surviving adults of a population that has been declining for decades. A shark you can find is not a shark that is doing well; it is a shark that is where it has always been, in smaller numbers, being counted by people who did not see the earlier ones.

SOUTH AFRICA REGULATES SEA FISHING SPECIES BY SPECIES, WHICH IS NOT HOW MOST COUNTRIES DO IT.

A recreational permit is the entry ticket and not the whole of it. On top of it sits a minimum size and a daily bag limit SET PER FISH, a closed season on a small number of species, and a cumulative daily cap across everything caught — so being inside the limit for each species separately does not put you inside the limit overall.

THERE IS A CAP ON HOOKS on a rod-and-line permit. A spearfishing permit is separate, allows no breathing apparatus beyond a snorkel, and PROHIBITS SPEARFISHING IN AN ESTUARY — a flat ban rather than a limit, and the rule visitors most often do not know.

A LANDED FISH MUST KEEP ITS HEAD AND TAIL so its length can be checked. Nothing caught on a recreational permit may be sold by anyone. And a small list of species may not be caught, landed or possessed at all.

FISHINGHQ DOES NOT PRINT THE FIGURES, and the reason is on this page rather than in a policy document: the department's own guidance says adjustments may be forthcoming given the acknowledged crisis of linefish, the numbers differ by species and by area and by whether you were standing on a beach or sitting in a boat, and a stale figure on a fishing site is worse than no figure at all. Get the current position from the Department of Forestry, Fisheries and the Environment, and get the protected-area position from whichever body manages the stretch of coast you are on.

Slow-growing, late-maturing and with about the lowest reproductive output of any fish an angler will meet: two pups per litter, roughly every second year. A population that loses adults recovers over decades if at all, which is the whole explanation for a Critically Endangered assessment on an animal that is still commonly seen in South African water.

INTRAUTERINE CANNIBALISM. The species is ovoviviparous with two uteri, and within each uterus the largest embryo consumes its siblings and then continues to feed on unfertilised eggs produced by the mother. The outcome is exactly two large, well-developed pups per litter after a gestation of nine to twelve months, with females breeding roughly every second year. South African populations migrate up the east coast to mate, with a well-documented seasonal pattern along the KwaZulu-Natal coast.

Takes fish, small sharks and rays, squid and crustaceans, gripping prey with the long narrow teeth and swallowing it whole or in large pieces. It is not equipped to cut, which is the mechanical reason it poses so little risk to a person. It hunts mainly at night and around dawn and dusk, and it will hunt cooperatively.

The standard shark suite — olfaction, lateral line, electroreception — with the addition of the air-gulping buoyancy control that lets it hang motionless and ambush rather than pursue. A shark that can hover is a shark that does not have to chase.

Strongly migratory along the South African east coast, moving north to mate and back again on a well-documented seasonal cycle. The aggregations on Aliwal Shoal and Protea Banks that support the dive industry are part of that cycle, which is also why area-based protection on those grounds matters for this species in a way it does not for a purely resident fish.

A regular capture in South African shore and boat shark fishing and the centrepiece of a substantial dive industry on the KwaZulu-Natal reefs. It is a recreational species at a strict daily bag limit with no minimum size, and it is Critically Endangered globally. Given two pups per litter every second year, the practical position is that a raggedtooth should be released, and released well.

RELEASE IT. A Critically Endangered animal that produces two pups every two years is not a fish to keep, whatever the bag limit permits.

DO NOT DRAG IT UP A BEACH. The body is supported by water and a large shark hauled onto sand is internally injured whether or not it swims away.

UNHOOK IN THE SHALLOWS with a long de-hooker, or cut the trace at the hook. Never a hand near the mouth: the teeth are for gripping and they grip.

CIRCLE HOOKS AND NON-STAINLESS HOOKS. A circle hooks in the jaw rather than the gut, and a corrodible hook left in a fish comes out on its own.

LAND IT QUICKLY WITH TACKLE THAT CAN. A long fight kills a released shark more reliably than anything else about the encounter.

AND DO NOT SIT ON IT, straddle it or hold it up for a photograph.