Thresher sharks (family Alopiidae) are an evolutionarily distinct and globally endangered species group. Indonesia is the world’s largest shark fishing nation, and a global priority for reducing the capture of threatened shark species. Kutaradja port is one of Indonesia’s largest fishing ports, located in the capital of Aceh Province, Banda Aceh, Western Indonesia. Kutaradja is a large oceanic port serving a variety of fisheries, from small scale to industrial fleets. One of the main fisheries operating from Kutaradja port is an industrial purse seine fleet targeting valuable pelagic fish, particularly tuna. Pelagic sharks such as threshers are vulnerable to capture in these fisheries, due to their co-occurrence with stocks of valuable pelagic species. Here we describe the volume and composition of shark catch in Kutaradja’s purse seine fleet, based on daily landing monitoring conducted in January 2017 to May 2019. Our results show that the dominant species caught are thresher sharks (Alopiidae), which make up 51% of all shark landings. A total of 627 thresher sharks were landed during the monitoring period, consisting of 558 individuals of pelagic threshers shark (Alopias pelagicus) and 69 individuals of bigeye thresher shark (Alopias superciliosus). The catch is dominated by mature females, which could be particularly detrimental to the reproductive capacity of the population. Fishers in purse seine vessels often catch these threshers with hand-lines, which are used as a secondary gear while the main fishing gear is soaking. Based on these findings, we proposed recommendations for reducing thresher shark fishing mortality, including restricting the use of secondary fishing gears and releasing incidentally captured sharks.

The waters of North Maluku Province are known as a hotspot for sharks in Indonesia. However, despite the richness and importance of shark population in this area, information about shark fisheries and trade remains limited. The aim of this research was to fill this knowledge gap by identifying the characteristics of shark fisheries and trade in this region. We conducted interviews and field observations during August 2017 in two case study regencies: South Halmahera and Morotai. The result show that targeted shark fishing is practiced in Mano village, Gomumu Island, South Halmahera and Posi-posi and Leo-leo Villages of Rao Island, Morotai Island. Mano village’s fishery consists of 48 vessels, with the main fishing grounds in Halmahera and Papua waters. Posi-Posi and Leo-Leo Villages operate a fleet of 12 vessels, within the main fishing ground in northern Morotai waters. We identified two traders of shark products in Morotai Island Regency, and seven traders in South Halmahera Regency. The primary traded commodities are shark fins and meat, predominantly. Fins are transported by boat to traders in Manado, Surabaya, Bau-Bau and Makassar, while meat is sold on to traders in Jakarta. We expect that the results of this research can be used to direct attention and resources towards managing shark fisheries and trade in North Maluku Province in the future.

Many shark species (Class Chondrichthyes) are threatened with extinction due to overfishing. Of the >1,000 described Chondrichthyan species, the pelagic thresher sharks (Alopias pelagicus) are of particular conservation priority since they are evolutionarily distinct and globally endangered. As the world’s largest shark fishing nation, with particularly high catch rates of thresher sharks, the impact of Indonesian fisheries has become a global priority for thresher shark conservation. Therefore, baseline data is needed to inform management and implement international environmental agreements such as the Convention on International Trade of Endangered Species (CITES). This research provides data and management recommendations for small-scale targeted shark fishing in Western Indonesia, where thresher sharks are regularly caught. Yet, fisheries are data-poor, with limited information on catch rates and limited regulation in place. Daily landings data was recorded from June 2019 to December 2020 in two sites in Southwest Aceh, and analysed to explore catch patterns, risk factors for thresher sharks, and potential mitigation options. The results show that 25 wooden vessels of <30 Gross Tonnage (GT) use bottom longlines to target sharks in the Indian Ocean. A total of 109 pelagic thresher individuals were recorded during the study period, with a female-skewed sex ratio (1 Female vs 0.39 Male), presumably impacting the population's reproductive potential. Based on this data, we offer some potential management measures to reduce fisheries impacts on pelagic thresher sharks by applying a simple mitigation hierarchy framework. These results offer fisheries management recommendations, including effort limits and gear modifications. Overall, the data we present could contribute to understanding the stock status and exploitation rate of thresher sharks in the Indian Ocean and support CITES implementation in Indonesia. At the same time, the mitigation hierarchy approach and recommendations could be applied to other similar small-scale fisheries in Indonesia and globally

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