Hand in hand: MPAs and fisheries management help reef sharks

Over the many years since marine protected areas (MPAs) were first designated, there has been lively debate about their value. Concerns have been raised about how efficiently they are managed and their restrictions enforced, as well as about conflict with fishers. Reservations have been voiced too about their effectiveness in view of the complexity of the ecosystems they encompass and the nomadic, roaming lifestyle of some of their inhabitants, notably the many shark species. Faced by the complex challenges of overfishing on a global scale and an ocean-wide extinction crisis, we are beginning to recognise the need for a suite of solutions – and MPAs are an important element of that suite.

A recent paper published in Nature Ecology & Evolution sheds light on how effective MPAs are in the conservation of vulnerable shark species. More than 100 authors contributed to the study, which covered 66 MPAs within a range of fisheries management regimes across 36 countries. The research demonstrated that fully protected areas can benefit reef-associated sharks significantly, but they alone are unlikely to be effective in conserving elasmobranchs (sharks and rays).

Global FinPrint, a survey making use of more than 18,000 baited remote underwater video (BRUV) systems, monitored coral reefs around the world. The images captured by these video systems revealed which sharks and rays occurred in the protected areas covered and helped to assess how these MPAs could be combined with fisheries management to benefit the conservation of reef-associated elasmobranchs.

The effectiveness of MPAs around the world varies depending on the culture, belief systems and practices of coastal communities, and the research determined that, of the countries studied, Belize, Australia and the Philippines are among those that support the more effective protected areas. It also concluded that the four most important factors that shape this effectiveness are: human impact (MPAs proved to be most effective for elasmobranchs in waters where human pressure is high); the isolation of reefs (MPAs that included reefs more than 20 kilometres, or 12.5 miles, apart were most effective); size (MPAs larger than 20 square kilometres, or 7.7 square miles, were most effective); and shark fishing bans (MPAs proved to be most successful in countries that also had a nationwide ban on shark fishing in place, thus merging two regulatory tools.)

Against a background of individual approaches to fisheries management, one of the unequivocal findings that emerged was that, taken in isolation, neither MPAs nor traditional management measures were as effective as a combined approach.

In fact, in other areas, where sharks still account for a portion of the catch, it was found that MPAs in waters where catch limits were implemented and harmful fishing practices such as the use of gill nets and longlines were banned, the conservation benefits were doubled compared with areas of ineffective fisheries management.

Shark species that spend most of their life cycle on coral reefs, such as Caribbean reef sharks, grey reef sharks, whitetip sharks and nurse sharks, benefited the most from protected areas, whereas rays (both small and large) and wide-ranging shark species seemed to derive little advantage from them. However, the low number of rays reported from MPAs may be a result of their aversion to areas with higher shark abundance, and wide-ranging shark species are highly mobile and would require fisheries management on a national or regional scale.

Although the priorities of many established MPAs do not specifically include the protection of elasmobranchs, protected areas are still helping to replenish certain reef shark populations. As studies such as this reveal more about the impacts of MPAs, we are gaining a more holistic understanding of the role that MPAs might play in curbing the extinction crisis faced by both teleosts (bony fish) and elasmobranchs. Local communities are key to the success of these measures and they should be integrated into the design and management of MPAs; human well-being and the health of our ocean are, after all, intrinsically linked.

This study shows that there are sound reasons to combine approaches to the management of MPAs and offers a solid foundation for future conservation efforts.

**Reference: Goetze JS et al. 2024. ‘Directed conservation of the world’s reef sharks and rays’. Nature Ecology & Evolution 8. DOI:10.1038/s41559-024-02386-9