Tuna fisheries are the most valuable fisheries in the world, with an estimated market value of at least US$42 billion in 2018. Indonesia plays an important role in the global tuna fisheries and has committed to improve its fisheries management; therefore, a pilot of long-term spatial-temporal data bases was developed in 2012, however none have utilized data to have better understanding for management improvement. In this study, the annual and seasonal variation of large (≥10 kg) Yellowfin Tuna (YFT) catch per unit effort (CPUE) have been investigated and the influence of sea surface temperature (SST) and chlorophyll-a on these variables examined. We used fish landing data from West Nusa Tenggara recorded every month between 2012 and 2017 and analyzed using generalized linear models and generalized additive models. We found a seasonal and annual pattern of tuna abundance affected by SST and chlorophyll-a (chl a) and related to upwelling and El Nino event. These results also suggest that a two-month closure to fishing in August and September in southern Lombok is worth considering by the Government to maximize conservation of stocks due to a high abundance of juveniles emerging during the upwelling months from June to August.

There are millions of small-scale fishers worldwide that rely on coral reefs for their livelihood. Yields from many of these coral reef fisheries, however, have been declining. In Indonesia and other coral reefs worldwide, management approaches are dominated by marine protected areas but other options including gear-restrictions may be feasible and more adaptive to local ecological and social conditions. Yet, there is little data on the impacts and selectivity of fishing gears for coral reef fisheries. In this paper, we present results from a case study on the island of Lombok, where we examine the selectivity and overlap in catch composition of the two main fishing gear types: spearguns and handlines. The catch per unit effort (CPUE) was greater in handlines than spearguns, 10.8 and 9.97 kg trip^-1, respectively. The two gears targeted different fish communities with little overlap in dominant species, suggesting a partitioning of resources; handlines targeted piscivores, whereas spearguns targeted mostly herbivores. Mean trophic level was 3.6 for the handline catch and 2.8 for spearguns, where it was inversely related to CPUE. Spearguns captured more species overall and the number of species increased as the CPUE increased. Length parameters of maturity indicated that neither gear showed signs of (growth) overfishing and fishing grounds dominated by speargun fishers had catches associated with younger ages at first maturity than handlines. Our findings provide local baseline data on the potential utility of gear restrictions as a management tool. Specifically, managers could monitor reefs and reduce handlines when piscivorous fishes are low and on spearguns when species diversity is low or algal abundance is high. Should it become more desirable to implement ecosystem approaches to management that are adaptive to changing ecological and social conditions, these indicators may be used as starting points along with local management preferences of fishers.

Overfishing is a major threat to the survival of shark species, primarily driven by international trade in high-value fins, as well as meat, liver oil, skin and cartilage. The Convention on the International Trade in 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 efforts to ensure that trade does not threaten their survival. However, as international trade regulations alone will be insufficient to reduce overexploitation of sharks, they must be accompanied by practical fisheries management measures 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 effort depended primarily on the number of hooks and type of fishing gear used, and to a lesser degree on month, boat engine power, number of sets and fishing ground. The most significant factors influencing the likelihood of catching threatened and regulated species were month, fishing ground, engine power and hook number. We observed significant negative relationships between standardised catch per unit effort and several indicators of fishing effort, suggesting diminishing returns above relatively low levels of fishing effort. Our results suggest that management measures focusing on fishing effort controls, 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.

Manta rays ( Mobula birostris and M. alfredi ) are threatened by overexploitation for international trade. Indonesia was home to the world's largest documented manta fishery—Lamakera, in East Nusa Tenggara. However, in 2014, the Indonesian government declared manta rays a protected species. Here we describe an integrated intervention to reduce manta hunting and mortality in Lamakera, which combined community outreach and livelihood‐focused incentives with targeted enforcement actions; and assess its impact over a five‐year period (2013–2018) using a theory‐based research design. Results show that the intervention is associated with a significant decline in manta hunting effort and mortality ( p < .001), which is correlated and temporally‐associated with conservation activities, and did not occur for modeled and natural experiment counterfactuals. Overall, total manta ray mortality declined by 86% by 2018, vs. the 2013 baseline. We conclude that a multifaceted, data‐driven approach reduced illegal hunting and trade of manta rays from 2013 to 2018. However, this impact is not indefinite; new challenges are emerging, which highlight the importance of a long‐term adaptive strategy. We make several recommendations for designing interventions to mitigate trade‐driven over‐exploitation of megafauna: (a) understand diverse drivers of human behavior; (b) adopt data‐driven problem‐oriented planning; (c) continuously document and share learning; (d) establish partnerships with diverse stakeholders to develop resilient institutions for enduring impact.