Western and Central Pacific Ocean tuna: sharks and rays handling and release techniques

• Evaluate post-release survival rates for sharks and rays
• Collect and analyse data to estimate post-release mortality
• On board training of fishers to optimise tag and release techniques and data collection
  

Tuna fishery interactions with sharks and rays

The fleets of Papua New Guinea Fisheries Industry Association (PNG FIA) and Tri Marine represent a significant segment of purse seine operations in the Western and Central Pacific Ocean (WCPO).

Fishing operations can interact with several non-target species, including silky sharks (Carcharhinus falciformis), oceanic whitetip sharks (Carcharhinus longimanus), and mobula rays. Incidental captures are of great concern due to the ecological importance of such key predatory species in marine ecosystems. Sharks and rays are also of cultural and economic significance in the region.

Tri Marine and PNG FIA are certified to the MSC Fisheries Standard. As a condition of their certification, they must provide evidence that they are minimising their impacts to endangered, threatened and protected (ETP) species. The fisheries have adopted and enhanced bycatch mitigation devices but need to provide evidence on the post-release survival of shark and ray bycatch.

To retain their sustainability certification and meet regional fisheries management organisation regulations the fisheries are now involved in a project, designed and managed by the International Seafood Sustainability Foundation (ISSF). It is this project that has been selected for a Science and Research Fund grant from the MSC Ocean Stewardship Fund.

What the project will do

The project will evaluate post-release survival rates for sharks and rays when handling and release best practices are used, through tagging with satellite transmitting tags. 

A cruise with a scientist on board, as well as fishers trained under the project, will gather data and tag released sharks. A total of 30 sharks and mobula rays will be tagged.

Additional data - such as stress indices, release methods, and operational and environmental factors - will be analysed to estimate post-release mortality. Results will inform improved handling guidelines that can be applicable to other fisheries in the region and around the globe.

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