Grey nurse shark
Pregnant grey nurse sharks at Wolf Rock Photo: C Bansemer
Common name: grey nurse shark
Scientific name: Carcharias taurus
Conservation status: The grey nurse shark is Endangered in Queensland (Nature Conservation Act 1992).Two separate populations of grey nurse shark are listed under the Environment Protection and Biodiversity Conservation Act 1999, with the east coast population listed as Critically Endangered. It is also considered a high priority for conservation under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
The grey nurse shark has a fusiform (ie spindle-shaped), moderately stout, bronze body with a pale undersurface. Brownish spots appear on the upper body and tail fin, although some individuals may lack obvious spots. The first dorsal fin is closer to the pelvic fins than to the pectoral fins. Five gill slits extend below the base of the pectoral fin. The two dorsal fins are almost equal in size.
Habitat and distribution
The grey nurse shark is known to occur on the continental shelf mostly from the surf zone down to at least 190 m in depth. At sites where they aggregate, they are often observed near the bottom at depths of 10 – 40m in or near steep-sided gutters with sandy substrata, or in rocky caves. Grey nurse sharks have also been observed congregating in mid-water adjacent to, or above pinnacles or wrecks at depths of 5 – 30m. Within Australia there are two populations of grey nurse shark - one is found in coastal waters of Queensland and New South Wales (NSW), and the other in Western Australia. The east coast grey nurse shark population extends from mid-Queensland to Narooma in southern NSW and their distribution and movements within this range vary with age, sex and reproductive state.
Approximately 50% of pregnant sharks in the east coast population spend most of their 9-12 month gestation (pregnancy) at Wolf Rock, off Rainbow (the most northern known grey nurse shark aggregation site in eastern Australia) before heading to mid-southern NSW to pup. They remain there for 1–2 rest years and then return to Queensland waters to mate and gestate. Where the other 50% of pregnant grey nurse sharks gestate remains a mystery, but research is underway to locate the missing aggregation site/s.
Every year, from late autumn, mature male sharks move north (from central–southern NSW) and mate in late spring/early summer in warmer Queensland waters, returning afterwards to NSW.
In contrast to mature animals whose distribution and movement patterns vary with reproductive activities, the majority of immature sharks of both sexes restrict their movements to the central to southern parts of the grey nurse shark’s east coast range. Immature sharks also often segregate from their mature counterparts.
Life history and behaviour
Grey nurse sharks are thought to live for between 30 and 40 years, grow to about 3.2m in length and are relatively slow to mature. Female sharks mature at between 2.2 and 2.6m (9-10 years) and males between 1.9 and 2.2m (6-7 years). They have a low reproductive rate with a gestation period lasting 9-12 months and thought to occur every second year. Cannibalism occurs in the mother’s uteri, with embryos hunting and consuming other embryos until one remains in each of the two uteri. As a consequence, they usually give birth to only one or two pups, which are approximately 1m in length.
Grey nurse sharks are often observed in aggregations of five or more sharks. They primarily feed on a range of teleost (bony) fishes. They have also been reported to eat squid, crabs, lobsters and small elasmobranch (cartilaginous) fishes.
Grey nurse shark with fishing gear embedded in jaw and trailing from gill slit Photo: C Bansemer
The grey nurse shark is one of Australia's most endangered marine species with about 1000 individuals thought to remain within the east Australian population. The grey nurse shark was hunted almost to extinction during the 1950's to the 1970's due to its fierce appearance. Today, incidental capture by recreational and commercial fishing and mortality related to shark control activities are the primary threats to the Australian east coast population.
The Queensland Government introduced fishing and diving laws in Moreton Bay Marine Park and at Wolf Rock in 2003 to protect the grey nurse shark and its habitat.
Details of the grey nurse shark designated areas, which are also green zones, are provided in the Marine Parks (Moreton Bay) Zoning Plan 2008 and the Marine Parks (Great Sandy) Zoning Plan 2006 available from the Queensland Parliamentary Counsel website.
Where are the grey nurse shark areas?
There are three grey nurse shark areas in Moreton Bay Marine Park and one in Great Sandy Marine Park (datum GDA94).
- Cherub's Cave off Moreton Island (the area in a 1.2 km radius of the point 27007.67' south, 153028.67' east).
- Flat Rock off North Stradbroke Island (the area in a 1.2 km radius of the point 27023.41' south, 153033.07' east).
- Henderson Rock off Moreton Island (the area in a 1.2 km radius of the point 27007.92' south, 153028.71' east)
- Wolf Rock off Rainbow Beach (the area in a 1.5 km radius of the point 25054.600' south, 153011.850' east).
What are the diving requirements?
Grey nurse sharks and divers at Wolf Rock Photo: C Bansemer
Diving restrictions are in place to protect the grey nurse shark and its habitat.
Divers in the grey nurse shark areas must not:
- Dive between 6pm and 6am.
- Touch or feed a grey nurse shark.
- Chase, harass or interrupt the swimming patterns or interfere with a grey nurse shark's natural behaviour.
- Attempt to block cave entrances or gutters, or entrap grey nurse sharks.
- Use mechanical or electro-acoustic apparatus including, but not limited to, scooters, horns and shark-repelling devices (commercial operators may use equipment required for diving under the Work Health and Safety Act 2011).
- Dive as part of a group of more than 10 divers (tourist operators may have groups of up to 12 divers, provided the extra divers are either instructors or guides).
Divers can be fined for breaking these laws.
The Queensland Government may also develop a system to manage the number of divers visiting the areas where grey nurse sharks congregate. This may include setting distances between dive groups and limiting the number of groups that may use an area at a time.
These changes were introduced to protect the grey nurse shark and its habitat. However, there is scope to increase restrictions if further protection is needed for the species.
Are tourist operators affected?
Yes. Tourism operators with diving as an activity on their Marine Parks permit and dive clubs that are diving in a grey nurse shark area must do the following:
- Ensure that divers are given information about the restrictions for the zone and about entering or using the grey nurse shark area.
- Display the entry and use provisions for grey nurse shark areas in a prominent position on board all diving boats and in dive shops or clubs that operate or promote diving trips in Moreton Bay Marine Park. Tourist operators and dive clubs can be fined for breaking these laws.
Fines can be imposed for the unauthorised taking, using or keeping of any part of a grey nurse shark.
How can I help protect the grey nurse shark?
There are a number of ways you can help protect the grey nurse shark.
- Report injured, sick or dead grey nurse sharks to the RSPCA Qld on 1300 ANIMAL (1300 264 625)
- Join Grey Nurse Shark Watch and carry out opportunistic or scheduled volunteer visual and photographic surveys. For more information please refer to the Grey Nurse Shark Watch Factsheet.
- Make sure you comply with the fishing closures on aggregation sites and be aware that grey nurse sharks may be encountered elsewhere, particularly during migratory periods.
- When fishing, use corrodible, non-offset circle and/or barbless hooks (Recfishing Research National Code of Practice)
- Tell friends and family about grey nurse sharks.
For information about the management of grey nurse sharks in NSW key aggregation sites visit the New South Wales Department of Primary Industries (Fishing and Aquaculture).
For more information about grey nurse sharks visit the Department of the Environment Species Profile and Threats Database: Carcharias taurus Grey nurse shark (east coast population).