Thresher Sharks, Australia
The proposed study aims to assess thresher shark vulnerability to Australian fisheries using a combination of tagging, modelling, and social sciences techniques while linking with commercial and recreational fishers, and provide management recommendations if necessary.
Why this is important:
Thresher sharks (genus Alopias) have been listed as Vulnerable globally because of their declining populations (e.g., in the Northwest Atlantic where reported landings collapsed by 80% in the last 15 years). Some species of thresher sharks were also recently ranked at the highest risk of overfishing amongst 12 pelagic sharks and rays investigated.
Many countries fish thresher sharks commercially throughout their extensive ranges, with the common thresher (A. vulpinus) probably being the most commercially important species. The common thresher is a large, highly migratory pelagic shark with a cosmopolitan distribution in subtropical and temperate waters This species is especially vulnerable to fisheries exploitation (target and by-catch) because its epipelagic habitat occurs within the range of many largely unregulated and under-reported gillnet and longline fisheries, in which it is readily caught. It is an important economic species in many areas and is valued highly for its meat and large fins. Its life-history and high value in both target and bycatch fisheries make it vulnerable to rapid depletion. Serious declines have already occurred where this species has been heavily fished, for example in the Northwest Atlantic where reported landings collapsed by 80% in the last 15 years As a result, the species has been listed as Vulnerable globally under the IUCN Red List (Goldman et al., 2009).
A recent study using demographic analysis has shown that thresher sharks are extremely vulnerable to overexploitation and that they were especially sensitive at the juvenile and adult stages. The authors implied that nursery closures were urgently needed to ensure the sustainability of thresher shark populations. However, in order to do so, an improved understanding of thresher sharks movement dynamics and spatio-temporal residency patterns is required.
Unfortunately, few tracking studies have been conducted on thresher sharks with the only studies being on bigeye thresher (A. superciliosus) in the Pacific Ocean and on common threshers in the East Pacific Ocean. Virtually nothing is known regarding the vulnerability and movement patterns of the thresher sharks in Australian waters.
Aims and Objectives
General aim: Assess thresher shark vulnerability to the Australian commercial and recreational fisheries through a combination of literature review, database searches, survey techniques, and tracking technology.
This project will not solely collect biological data but use a combination of social and biological methods and involve the stakeholders which would be affected and have to implement potential fishing regulations (e.g., recreational and game fishers). This multi-disciplinary approach will allow simultaneous evaluations of the biological and social components and provide management and conservation recommendations based on broad information base. The project leader will also be engaging and working in collaboration with the stakeholders throughout the project who will provide logistic support to tag thresher sharks. This is a very different model than traditional projects that collect one type of data (e.g., either social or ecological) and disseminate the outcomes at a later stage.
SARDI – Aquatic Sciences / Flinders University
I was awarded an overseas fieldtrip grant as part of the Flinders University postgraduate grants program to travel to California to assist on a five-day leg of the juvenile thresher shark survey in September 2012. Scientists from the fisheries division…
Following an unsuccessful field season in early 2012 in which we were unable to deploy any satellite tags on common thresher sharks, we kicked this season off with a nine day field trip to Portland in Victoria. As part of…
Following the successful deployment of our first pop-up satellite tag in December 2012, we continued to target thresher sharks through the rest of the summer with high hopes. Between December and April, we fished for a total of 22 days,…