Lifeline for the much maligned grey nurse shark

A weekend citizen science census of grey nurse sharks has revealed “terrifying low” numbers of the iconic fish, the familiar silhouette of which has sparked 1000 scare campaigns of its own.

Scientists are monitoring habitat to put in place conservation programs. But it’s not only scientists helping these sharks: citizen science projects and the monitoring programs are crucial to the shark’s survival, according to conservation biologist Adam Stow who has studied the species for more than 20 years.

“It’s critically important, we need to know where they are [aggregation sites] and whether they’re changing,” he says. One of these citizen science projects employs photo identification (photo-ID) techniques to significantly increase the scope of research while reducing the cost of data collection, as well as supporting local tourism ventures and enhancing public education.

Besides unique spot markings on their flanking regions, grey nurse sharks can be identified by other important characteristics (e.g. jaw wounds, missing fin sections) in photographs. There are biannual surveys of grey nurse sharks (January to February and July to August) that take into account seasonal variation in their distribution and movement patterns, as well as opportunistic photography taken by divers throughout the year at some aggregation sites along the Australian east coast. 

The “Ocean Lover’s Festival” Grey Nurse Shark Census, which was conducted by multiple dive operators led by shark conservationist Valerie Taylor, counted 249 individuals in 20 different locations. “That number is terrifyingly low,” says Captain Gordon Scott, who coordinates the census, and who believes this is an alarm to get more effective protections passed – “what we currently have is not enough.”

Grey nurse sharks (Carcharias taurus) were falsely accused of being responsible for shark attacks off Sydney’s beaches in the 1950s and 60s. In response to their fierce appearance, grey nurse sharks were executed at every possible opportunity, resulting in the drastic decline of their population.

The shark’s numbers further diminished in the late 1970s, but after realizing that they were not “man-eaters,” lobbying for their protection began. In 1984, the New South Wales (NSW) government declared them a protected species, making them the first protected shark in the world. Today, they have “vulnerable” status globally and “critically endangered” in Australia under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act). Both State and Commonwealth levels have taken steps to list and protect grey nurse shark populations along the east (and west) coast of Australia.

In Australia, there are two separate populations recognised. One on the eastern coast of Australia between Northern NSW and Queensland, and the other along the coast of Western Australia. The eastern Australian population congregates at and moves between a few key sites along the coastline from Montague Island in the south to Fraser Island in the north of New South Wales and southern Queensland. Australia’s east coast has between 1,500 and 2,000 individual grey nurse sharks, but the breeding population here is worryingly just roughly 400 sharks; this lack of genetic diversity puts into question what the future holds for the predators.

Currently, scientists are following the national recovery plan in place for the species, which includes obtaining population size and animal movement data from a tagging program conducted primarily by New South Wales Fisheries, with supporting research from Queensland Parks and Wildlife Service and CSIRO staff.

A senior conservation officer with the Queensland Department of Environment and Science (DES), marine biologist Dr Carley Kilpatrick is part of a research team from DES and Sea World that uses tags to document important grey nurse shark habitats. One of these tags has prematurely popped off and since then has baffled researchers: it popped up about 600 kilometers off the east coast near Coffs Harbour area and then pinged in Boambee Bay a few hours later. “It could be in someone’s house, it could be buried in the sand, that one’s a real mystery but someone knows more about that tag,” Kilpatrick told ABC News. “Maybe someone’s been out there on a charter fishing [trip], caught a flight back to Coffs [Harbour] and then not known what to do with the tag and thrown it overboard.”

Researchers attach tracking tags to or near the dorsal fin and program them to pop off and float to the surface on a certain date, so they can transmit GPS signals and be retrieved. “We get a summary of data from a satellite transmission but if we get the tag back we get the full data set,” she said.

The confusing transmissions come from a tag that belonged to a male grey nurse shark, one of two tags which is currently missing. The second tag belonged to a sexually mature female which measured 2.8 m long. “We don’t know exactly what’s happened but it was floating around on the surface of the water and then it went silent,” Kilpatrick said.

This tag is particularly significant because the team hopes to gain a better understanding of the species to protect gestating females during migration.

Kilpatrick and her team also say the public is crucial in helping them uncover this tag mystery and are urging those who live in the area to keep an eye out for the tags and to contact DES (phone number 07 3101 2085) if anyone has any information on either tag.

More in The Weekly

Cybernetics: How does a futurist peer into the future?

By Mark Pesce

Maori knowledge changing the way New Zealand responds to disasters

By Rachel Williamson

The next COVID wave

By Deborah Lupton

The true story and history of the chicken

By Jonica Newby