There are three major areas of concern when it comes to sharks – observed bycatch, unobserved mortality due to entanglement in fishing gear, and waste from (and poor data about) finning.


The shark bycatch-to-tuna catch ratio in purse seine fisheries is small, on average, less than 0.5% in weight. But the global magnitude of catch of the purse seine fisheries is quite large, so reducing the shark mortality caused by these fisheries can positively impact global shark conservation efforts.


Each year, ISSF supports multiple initiatives to track, report on and minimize unwanted bycatch like sharks among purse seine fishing vessels, as well as conduct research across all fishing methods to define and promote best practices that positively impact this important issue. We also advocate for the adoption of mandatory shark bycatch data-collection and mitigation measures, appealing to the world’s tuna RFMOs for the adoption of science-based shark conservation and management measures.

To date, in cooperation with a number of partners from the tuna industry and the scientific and fisheries management community, ISSF has identified and disseminated a number of mitigation practices:
    • Employing best practices onboard vessels to release live sharks from the deck that can reduce the direct mortality of silky sharks by 15 to 20 percent; good practices are included in the ISSF Skippers’ Guidebook.


    • Avoiding setting on small schools of tuna (i.e. less than 10 tons), which can help fishers significantly reduce their catches of silky sharks by 20 to 40 percent, depending on the oceans; information on this mitigation measure is also included in the ISSF Skippers’ Guidebook.


    • Reducing entanglement under FADs through the use of non-entangling materials in the underwater hanging structure or by other procedures such as tightly wrapping hanging nets with ropes, which results in a tight cylinder (“sausage” or “chorizo”)

ISSF is currently investigating other methods to avoid encircling sharks or to release sharks from the net. Scientists, in partnership with purse seine vessel owners, are testing the use of escape panels to release sharks from the net, as well as whether the “backdown maneuver” used to release dolphins in tuna-dolphin aggregations could also be effective in releasing sharks and other bycatch.