Grey Nurse Shark
The Grey Nurse Shark (Carcharias taurus) has an unfortunate history along the east coast of Australia. In the 1950s and 60s they were thought to be responsible for the shark attacks off Sydney's beaches. Wrongfully accused because of their fierce appearance, the so-called "man-eating" Grey Nurse Sharks were executed on every possible occasion. The net result of the indiscriminate spearing was a dramatic drop in their numbers as evidenced by reduced numbers of Grey Nurse Sharks in the protective beach meshing program.
By the late '70s Grey Nurse Shark numbers had further dwindled and, with the realisation that the Grey Nurse Shark was not a "man-eater", lobbying for protection of the shark commenced. In 1984, the NSW government declared Grey Nurse Shark a protected species. In doing so, the Grey Nurse Shark became the first protected shark in the world. Despite this, surveys in 1991 and 1995 at Seal Rocks combined with further reduced catches in the protective beach meshing programs at Newcastle, Sydney and Wollongong suggested that the Grey Nurse Shark population had still not recovered.
Why would this be the case? The likely answer lies with the sharks bizarre reproductive biology. The Grey Nurse Shark is a live-bearer, with two pups born per litter. Although batches of up to 15 embryos start developing in each of the two uteri, the most advanced embryo in each uterus eats the remaining embryos in the batch, a phenomenon known as inter-uterine cannibalism. This is then followed by an 'oviphagous' phase in which the developing pups eat pea-sized eggs produced by the mother. The gestation period is also very long, lasting from 9 to 12 months with birth occurring when the pups are about one metre in total length. More importantly, research in the USA and South Africa has shown that females have a resting stage of about a year, with pupping occurring every second year. Consequently, only one pup per female is produced per year, on average.
With this in mind and the reduced catches in the beach meshing program, NSW Fisheries initiated a research project to quantify the numbers of Grey Nurse Sharks along the NSW coast and examine ways of enhancing the shark's conservation. In early 1999, shortly after the research program commenced, the Grey Nurse Shark was declared a Threatened Species with "Vulnerable Status under the Fisheries Management Act.
To accomplish the coastwide surveys, we enlisted the help of scuba divers from universities, dive clubs, commercial aquaria and the commercial diving industry. With the scuba diving community's involvement, for which we are very grateful, it was possible to cover the entire coast from Eden to Tweed Heads and into southern Queensland (Stradbroke Island) sampling 50 to 60 sites along the entire NSW coast. To our knowledge these surveys are the first of their kind in the world because of the large community input focussing on the conservation of a shark.
The survey required that divers make visual observations over a 15 minute period at the chosen sites. When Grey Nurse Sharks were present the divers recorded the total number of individuals, their sex and estimated their length. Several surveys have now been completed with only 207 Grey Nurse Sharks observed in the 1999 winter period. More than half the sites had no Grey Nurse Sharks, 13 sites had aggregations of 5 or more (totalling over 100), while the rest of the sites had just one or two individuals.
The results of these coastwide surveys suggest that the Grey Nurse Shark population in NSW waters has not recovered since it was made a protected species and thus clearly support the declaration of the Grey Nurse Shark as Threatened. The next phase of the research will involve further surveys, tagging and an evaluation of the role of Marine Protected Areas in enhancing the conservation of the Grey Nurse Shark.