By Hollie Booth and Irfan Yulianto
November 14, 2018
Sharks and their cartilaginous relatives are one of the oldest and most diverse species groups in the world. There are more than 1,000 described species, ranging from the tiny deep-water dwarf lanternshark, to the world’s biggest fish, the whale shark.
Sharks generally exhibit conservative life history strategies, which means they are slow-growing, long-lived, and produce few offspring. This makes them particularly vulnerable to over-exploitation from fishing pressure. In addition, sharks are currently caught in large numbers across a wide range of fisheries and gear-types, and for a wide range of reasons — including high value, accidental catch and for food security.
From accidental bycatch in artisanal gillnet fisheries, to targeted catch in commercial longline pelagic fisheries, it is now estimated that the global annual fishing mortality of sharks exceeds 100 million individuals per year.
This combination of ecological vulnerability and high fishing pressure has led to sharks and their relatives becoming one of the most threatened species groups in the world, with approximately one quarter of shark species now threatened with extinction. It is widely acknowledged that overfishing represents the greatest threat to their survival, and that improved fisheries management measures can reduce global shark fishing mortality.
This is a particular priority in Indonesia — the world’s largest shark fishing nation, where some shark species, such as the largetooth sawfish, are already thought to be functionally extinct due to overfishing.
However, with such a wide range of species, fisheries and socio-economic drivers, figuring out the most effective fisheries management measures is incredibly challenging, especially with the added complexity of managing trade-offs between conservation objectives and the socioeconomic importance of global fisheries.
This week, researchers from WCS Indonesia published a paper in PLOS ONE that sheds some light on this difficult question. In their paper, Irfan Yulianto and colleagues analyse two years of daily landings data from one of Indonesia’s most well-known shark fisheries (Tanjung Luar, in East Lombok, West Nusa Tenggara) to identify fisheries management measures for reducing catch of threatened and internationally regulated species.
The findings indicate that gear restrictions (in particular, reducing the number of hooks permitted on each fishing line) — coupled with time/area closures (e.g. marine protected areas) and precautionary catch or effort limits — could reduce mortality of threatened and protected shark species, such as threshers, hammerheads and silky sharks.
These measures, while reducing total fishing mortality, would also increase the overall cost effectiveness of the fishery, since catch per unit of fishing effort was found to peak at low-to-moderate levels of fishing effort.
“Better management of this fishery in the future is essential, not only to protect shark species and sustain healthy shark populations in Indonesia, but to maintain the well-being of the thousands of people who depend on shark resources in East Lombok for income, employment, and food security.” — Dr. Irfan Yulianto, WCS Indonesia Fisheries Program Manager
WCS Indonesia is working closely with the Indonesian Ministry of Marine Affairs (MMAF) — along with local government, fishers, and traders in East Lombok — to use these findings in the development of fisheries management regulations. A provincial-level working group for shark fisheries management has already been established. It meets this week to discuss the future of shark fisheries management in West Nusa Tenggara.
Overall, a range of approaches are required to improve regulation and management of shark fishing, and these approaches need to be adapted to specific species, fisheries and socio-economic contexts if they are to be effective and ethical. The findings of Yulianto et al. provide just one example for a particular fishery, but these measures may also be applicable to similar shark fisheries in other parts of Indonesia and beyond.
Other important measures for combatting unsustainable shark fishing include finning bans, restrictions on destructive and/or non-selective fishing gears, and species-specific bans or quotas, with mandatory catch mitigation measures and live release protocols.
Strengthening stock assessments, on-board and landing-site monitoring, and traceability of onward trade are also essential for enforcement and science-based management. Crucially, policy- and market-based instruments are required to incentivise the entire fishing industry to adopt responsible fishing practices and by-catch mitigation measures, particularly for the most vulnerable species.
If widely adopted and well implemented, such approaches can ensure that sharks deliver long-term benefits for people and ecosystems through multiple uses and values, including fisheries and tourism. This can enable the delivery of international environmental commitments, for example under UN Conventions on the International Trade of Endangered Species of Wildlife Flora and Fauna (CITES) and Biological Diversity (CBD), and the UN Sustainable Development Goals.
As per commitments made at Our Oceans 2018 in Bali in late October, this would ultimately preserve the health of shark populations and ocean ecosystems, as a legacy for future generations.
As Pak As Syamsudin, Chief of Tanjung Luar fisheries auction place for the East Flores fisheries department, stated, “Shark regulation is not only for sharks themselves, but also for humans. I want my grandchildren to be able to see sharks in Indonesia before they disappear like the sawfish.”