Protecting sharks across global fisheries cannot depend on a single action

Written by on June 26, 2015 in Other News, Sharks

By John D. Filmalter, Laurent Dagorn and Victor Restrepo

Mako shark.

Mako shark. Photo credit: NOAA.

Conservation in fisheries cannot be based solely on one type of action. A common occurrence is that a prohibition needs to be accompanied by some sort of monitoring and enforcement mechanism in order to be effective. This is especially important for activities that cannot be monitored back in port, e.g., through sampling of the landings.

A recent article by Travassos-Tolotti et al. (2015) highlights this issue in terms of the conservation measure that tuna RFMOs (regional fisheries management organizations) have passed to prohibit the retention of certain shark species. A ban on retention and sale of a species should work as a disincentive to any sort of targeting. But, as the authors show, a prohibition like this alone may or may not be effective in reducing mortality. To be effective, it needs to be combined with high observer coverage and mitigation measures.

Sharks are incidental catch in tropical tuna purse seine fisheries. The shark bycatch-to-tuna catch ratio in purse seine fisheries is quite small, on average less than 0.5% in weight (Restrepo et al., 2014). Nevertheless, because of the magnitude of purse seine fisheries, shark bycatches can be substantial, and any efforts to reduce that mortality can contribute towards conservation.

Through research and advocacy, the International Seafood Sustainability Foundation (ISSF) makes considerable efforts to strengthen and complement the shark possession bans adopted by the RFMOs. These include:

Non-entangling FADs. Based primarily on observations collected during ISSF research cruises, Filmalter et al. (2013) found that substantial unobserved shark entanglement can occur if large-mesh netting is used for the submerged structure of FADs. ISSF has developed guidelines for the construction of non-entangling FADs and has been a strong advocate for the adoption of mandatory non-entangling FAD requirements by the RFMOs.

Shark fins.

Dried shark fins. Photo credit: chooyutshing via photopin cc.

No shark finning. Shark finning is the practice of cutting the fins off and discarding the carcass at sea. This practice is not only wasteful, but it also reduces the accuracy of catch statistics (amounts, species identifications) that scientists need to accurately assess all impacts of fishing on these shark populations. ISSF advocates for RFMOs to prohibit shark finning and adopt measures requiring sharks be landed with fins naturally attached. ISSF has also adopted a market-based resolution to prohibit shark finning by purse seine vessels.

Best handling practices. Research funded by ISSF has shown that at least 15% of the sharks brought onboard purse seine vessels can survive if they are appropriately handled and released. ISSF develops and then shares best handling practices with skippers and crew through workshops that have been attended by more than 700 skippers and crew. ISSF also makes these best practices publicly available in electronic form in 10 languages.

100% observer coverage. ISSF believes that observer coverage is critical for many reasons, including the collection of valuable data on bycatch, such as sharks. Observers can monitor if measures such as a retention ban are being complied with. ISSF has also adopted a market-based resolution to require 100% observer coverage in large-scale purse seine vessels.

Bycatch mitigation research. ISSF conducts other research on bycatch mitigation, with a strong emphasis on sharks. ISSF is testing techniques to release sharks before they are brought onboard, which should maximize survival. In addition, ISSF is studying shark behavior around FADs, which could provide insight into other mitigation actions.

There are no “single bullet” solutions to fisheries issues. We believe that all measures, including possession bans, need to be carefully complemented by other measures if they are to be effective.


Dr. John Filmalter is a postdoctoral research fellow at the South African Institute for Aquatic Biodiversity. He has been working on the behavior of species associated with fish aggregating devices (FADs) for the past seven years, conducting fieldwork from purse seine vessels in the Indian and Pacific oceans.

Dr. Laurent Dagorn is a French senior scientist working for the Institut de Recherche pour le Développement. He has been working on FADs, with a special emphasis on the behaviour of fish at these FADs, for over 20 years. He has spent about 12 years in the Pacific (French Polynesia, Hawaii, California) and Indian (Seychelles, La Réunion) oceans, collaborating with various scientific organisations.

Dr. Victor Restrepo is Chair of the Scientific Advisory Committee for the International Seafood Sustainability Foundation (ISSF), a global coalition of scientists, the tuna industry and World Wildlife Fund (WWF), the world’s leading conservation organization, promoting science-based initiatives for the long-term conservation and sustainable use of tuna stocks, reducing bycatch and promoting ecosystem health. Previously, he worked with the International Commission for the Conservation of Atlantic Tunas and holds a PhD in Population Dynamics from the University of Miami.


Filmalter, J.D., M. Capello, J.L. Deneubourg, P.D. Cowley, and L. Dagorn. 2013. Looking behind the curtain: quantifying massive shark mortality in fish aggregating devices. Frontiers in Ecology and the Environment 11: 291-296.

Restrepo, V., L. Dagorn, D. Itano, A. Justel-Rubio, F. Forget, and J.D. Filmalter. 2014. A Summary of Bycatch Issues and ISSF Mitigation Initiatives To-Date in Purse Seine Fisheries, with emphasis on FADs. ISSF Technical Report 2014-11. International Seafood Sustainability Foundation, Washington, D.C., USA.

Travassos-Tolotti, M., J.D. Filmalter, P. Bach, P. Travassos, B. Seret, L. Dagorn. 2015. Banning is not enough: The complexities of oceanic shark management by tuna regional fisheries management organizations. Global Ecology and Conservation 4: 1–7.

Copyright © 2015 by Marine Science Today, a publication of Marine Science Today LLC.


If you enjoyed this article, subscribe now to receive more just like it.

Subscribe via RSS Feed Find MST on Instagram Connect with MST on Google Plus

1 Reader Comment

Trackback URL Comments RSS Feed

  1. E R Mingiant says:

    As the writers point out, sharks are only a very small percentage of the tuna purse-seine catch. But sharks are a large percentage of the tuna longline catch. It would be interesting to know what solutions the writers would propose for the longline fishery to mitigate its even greater impact on oceanic shark populations.