The grey nurse shark

Get the word “shark” out of your head for a moment and look at the animal. The grey nurse runs big and heavy through the shoulders, with a blunt snout and a mouth that never quite shuts over a bristle of long, thin, backward-curved teeth, so that it seems to grin at you with a jawful of ragged spikes. It is the shark of every bad dream. It is also one of the gentlest fish in the sea: an unhurried hunter of other fish and rays that spends its days hanging almost motionless above a reef, trimmed to a neat weightlessness by a bellyful of air it gulps at the surface and holds down. Divers queue up to swim with it because it could not care less that they are there. For most of the last century, though, hardly anyone bothered to look past the grin, and the grin nearly finished it off. It was speared for sport and shot as a “man-eater” on the strength of its face alone, until the east-coast population had dwindled to a scattered remnant. Today Carcharias taurus is listed Critically Endangered, among the most imperilled sharks in Australian waters, its mature east-coast animals numbering only in the low hundreds.

Geography, not diet, holds the grey nurse in place. All year round the sharks gather at a handful of well-known aggregation sites: rocky reefs and old volcanic pinnacles with sheltered, sandy-floored gutters and overhangs where they can hang out of the current in loose, hovering company. The most important on this coast lies at its northern end. Wolf Rock, a knot of pinnacles rising out of deep water off Double Island Point, sits at the seaward edge of the Cooloola sand mass. And Wolf Rock is more than a gathering place. It is the only spot on the east coast where pregnant females are known to see out their term, drawing a large share of the population’s breeding mothers into a few square kilometres of sea.

That concentration is the danger. A shark tied to a handful of gutters is exposed the way any animal is when its life funnels through a few irreplaceable addresses. Disturb, overfish or foul even one site and you do not lose a few individuals; you take a chunk of the future breeding stock at a stroke. The same is true on land (see species dependence). It is why Wolf Rock is now closed to fishing outright, a no-take green zone inside the Great Sandy Marine Park.

The grey nurse can spare nothing, because it breeds more slowly than almost any shark alive. Inside the mother the strongest embryo turns cannibal and eats its siblings, so a female delivers just one or two big, well-started pups, and only every second year. That is a trickle. The rate of increase is so slow that a knocked-down population takes decades to climb back, and it forgives little loss of adults to net or hook.

The aggregation reefs sit where they do for a reason. These current-swept pinnacles stand in the warm flow of the East Australian Current, on the stretch of coast where tropical and temperate life share a single rock. That is productive, structured water, and it draws big predators as surely as it draws the mingled reef fauna. So a docile, slow-breeding animal now depends on our restraint. For all its teeth, the monster was never the shark.