Eastern grey nurse shark population abundance and trend

Research funded by the Marine Biodiversity Hub (a forerunner of the Marine and Coastal Hub) and led by CSIRO and the New South Wales Department of Primary Industries (NSW DPI) provided the first robust estimate of adult abundance. The eastern grey nurse shark adult population was estimated at 2000 (950–3100), with the population trend increasing at 3% a year. Based on this finding, the research leaders concluded that existing recovery actions were effective, but that measures in place – such as protection of aggregation sites from all forms of fishing to protect the shark from incidental capture – should not be removed.

Recreational fishers and the aquarium trade have been liaising with NSW DPI on the easing of restrictions in light of the potentially improved population status of the grey nurse shark. Before this could be considered, the existing population estimate needs to be revised by incorporating new estimates of species length, age and growth.

This project will refine the abundance and trend estimate for the eastern Australian population of grey nurse shark and proposes to examine the shark’s expansion range into Victorian waters (evidence suggests the shark may now range as far west as Wilsons Promontory).

Approach

The project will incorporate technical advances such as epigenetic ageing, and collect additional samples using improved protocols to obtain more precise length measurements of grey nurse sharks. Specifically, it will:

• collect contemporary tissue samples from juveniles and adults and use stereo video analysis to obtain accurate length estimates;
• use growth curves derived from Australian grey nurse shark samples involved in the NSW DPI ageing project;
• examine ‘allowable take’ scenarios to underpin discussions on restocking public aquaria with grey nurse shark and determine whether current protection measures require changing; and
• investigate epigenetic ageing (degree of ageing based on patterns of DNA methylation) of juveniles using tissue samples from grey nurse shark with vertebral age (collected by NSW DPI).

Indigenous participation

The project will provide opportunities for Indigenous participation in field surveys, as well as skills transfer opportunities. This will build the capacity among sea rangers to assist with future monitoring.

In NSW, Aboriginal engagement as part of the grey nurse shark tissue sampling component from the wild population will involve providing sea-time experience and on-water training for Gumbaynggirr and Yaegl coxswain trainees. This capacity building is supported through NSW Marine Estate Management Strategy and coordinated through the Coffs Harbour and District Local Aboriginal Land Council (Garby Elders rangers program) and the Yaegl Local Aboriginal Land Council.

There is also potential for skills transfer with Indigenous clans in Victoria’s Gippsland region (the Brataualung, Tatungalung, and Krauatungalung peoples) and Indigenous Joint Management Rangers from the Gunaikurnai Land and Waters Aboriginal Corporation further to the west of Wilsons Promontory.

Expected outcomes

The findings of this project will provide a more precise estimate of the abundance of Australia’s eastern grey nurse shark population, and reduce uncertainty surrounding the trend in abundance. The Australian and New South Wales governments will have a stronger evidence base for making decisions about the species’ recovery and conservation.

Project location

Worimi (Broughton Island, Seal Rocks and Forster, NSW; Biripi (Cod Grounds and Southwest Rocks, NSW); Gumbainggir (Coffs Harbour, NSW); Krauatungalung, Tatungalung and Brataualung (Gippsland, Victoria) and Nipaluna (Hobart, Tasmania).