Ecological insights to inform management of shark catches in Muncar, Indonesia

Abstract

Shark populations face global declines, primarily as a result of overfishing. These declines threaten marine ecosystems and require urgent conservation attention. Despite advances in global regulatory frameworks, catch rates of threatened and CITES-listed sharks remain high. Indonesia, as the world’s largest shark-fishing nation, is a priority country where fisheries management is needed to halt and reverse shark population declines. This study investigates the operational and ecological characteristics of shark fishing in Muncar, East Java, a major shark fishing hub in Indonesia, to derive sustainability indicators and inform management strategies. We utilized daily landings data and spatial analysis to examine the overall state of the fishery, derive simple size-based sustainability indicators, and identify spatial, temporal and operational predictors of catches of threatened species as leverage points for management. Our results highlight that shark catches are dominated by threatened species, including the silky shark Carcharhinus falciformis , scalloped hammerhead Sphyrna lewini , spinner shark Carcharhinus brevipinna , blacktip reef shark Carcharhinus melanopterus and pelagic thresher shark Alopias pelagicus , with large proportions being caught before they reach sexual maturity. By analysing patterns across operations, space and time, we identified high-risk fishing gear, areas and seasons, which can inform targeted and effective management strategies. Our findings underscore the need for better fisheries management to halt population declines and implement CITES regulations in Indonesia. These include restrictions on the size of sharks that can be caught, catch limits or quotas and seasonal closures, integrated with measures to meet local socio-economic needs. We provide actionable insights for balancing conservation priorities with fishery economics, contributing to long-term ecological and community resilience.