PREDATORS AS PREY

GLOBAL DECLINE OF SHARKS

Published in January 2021, the first global census of shark and ray populations revealed that the abundance of these species has plummeted by more than 70 per cent since 1970. This decline has been more rapid in tropical waters than in temperate zones. A separate study of Queensland’s coastal reefs found that numbers of large sharks, including great whites, tigers and hammerheads, fell by at least 75 per cent during the same period.

So rapid and sustained has been this alarming depletion that it has pushed many species to the brink of extinction. Half of the world’s 31 oceanic shark species are now listed as endangered by the International Union for Conservation of Nature (IUCN), with three of them (oceanic whitetip, scalloped hammerhead and great hammerhead) classified as critically endangered. Four of the endangered species (pelagic thresher, dusky shark, shortfin mako and longfin mako) are rapidly declining in Australian waters but are still legally fished.

There are numerous pressures on shark populations, including ship strikes, oil and gas drilling, climate change, pollution, habitat degradation, control programs (culling, drum lines), and the impact of fisheries on the seabed and prey species. But the single biggest threat is over-exploitation by targeted commercial fishing (legal and illegal), incidental bycatch and ‘finning’.

OVERFISHING AND BYCATCH

Since the 1970s, fisheries have spread rapidly across the world. Fishing fleets have grown bigger, and advances in technology and equipment enable the modern industry to fish harder and further afield. In the past, only a few oceanic shark species were targeted, primarily for their high-value meat. But, due to the high and growing demand for