Southern Bluefin Tuna (SBT) is an iconic species both domestically and internationally. The most recent stock assessment estimated the spawning stock biomass at 9 per cent of unfished levels. SBT is listed as conservation dependent under the Environment Protection and Biodiversity Conservation Act, endangered in New South Wales and threatened in Victoria. The stock is subject to an international rebuilding plan under the Convention for the Conservation of Southern Bluefin Tuna.
Recreational fishing for SBT spans over 6,500 kilometres of Australia’s coastline and recreational fishing activity can be dispersed and episodic. Dedicated surveys for estimating SBT catch have occurred in Victoria and Tasmania with catch statistics for the other states coming from general angler surveys. SBT fishing is a low frequency activity and this characteristic has restricted the inference on total catch of SBT from general angler surveys. Hence, the total national recreational catch has never been quantified with the reliability needed for fisheries management.
A project to develop methods for estimating the national recreational catch of SBT has been completed. The project reviewed survey options and trialled an on-site stratified random access point survey in South Australia. Data from this trial, expert angler interviews, and commercial catch was used to model and test various sampling strategies. The methods used to develop an optimal survey design for estimating SBT catch in Australia have application more generally for designing recreational angler surveys when disparate sampling frames and episodic fishing activity are present.