Practical measures for sustainable shark fisheries: Lessons learned from an Indonesian targeted shark fishery

Overfishingis a major threat to the survival of shark species, primarily driven by international tradein high-value fins, as well as meat, liver oil, skin and cartilage. The Convention on the International Tradein Endangered Species of Wild Fauna and Flora (CITES) aims to ensure that commercial trade does not threaten wild species, and several shark species have recently been listed on CITES as part of international effortsto ensure that trade does not threaten their survival. However, as international traderegulations alone will be insufficient to reduce overexploitationof sharks, they must be accompanied by practical fisheries managementmeasures to reduce fishing mortality. To examine which management measures might be practical in the context of a targeted shark fishery, we collected data from 52 vessels across 595 fishing trips from January 2014 to December 2015 at Tanjung Luar fishing port in East Lombok, Indonesia. We recorded 11,920 landed individuals across 42 species, a high proportion of which were threatened and regulated species. Catch per unit effortdepended primarily on the number of hooks and type of fishing gear used, and to a lesser degree on month, boat engine power, numberof sets and fishing ground. The most significant factors influencing the likelihood of catching threatened and regulated species were month, fishing ground, engine powerand hook number. We observed significant negative relationships between standardised catch per unit effortand several indicators of fishing effort, suggesting diminishing returnsabove relatively low levels of fishing effort. Our results suggest that management measures focusing on fishing effortcontrols, gear restrictions and modifications and spatiotemporal closures could have significant benefits for the conservation of shark species, and may help to improve the overall sustainability of the Tanjung Luar shark fishery. These management measures may also be applicable to shark fisheries in other parts of Indonesia and beyond, as sharks increasingly become the focus of global conservation efforts.