Exploring cost-effective management measures for reducing risks to threatened sharks in a problematic longline fishery

Many shark and ray species (Class Chondrichthyes, herein ‘sharks’) are threatened by overfishing. Tackling this requires implementation of context-specific fisheries management measures, which are both technically effective and socio-economically feasible. Here we explore the cost-effectiveness of various input-oriented management measures for mitigating capture of seven priority shark taxa (i.e., threatened and CITES-listed species) in a small-scale longline mixed-species shark fishery in Indonesia, where there is a need to balance difficult trade-offs between conservation and socio-economic objectives. We apply Boosted Regression Trees (BRT) to analyse five years of landings and profit data, to identify and assess the relative influence of different plausible management measures (e.g., effort restrictions, gear restrictions, spatio-temporal closures). We then use predictive models to inform a semi-quantitative assessment of the hypothetical cost-effectiveness of these management measures, based on the estimated conservation benefits (reduced risk of capture of priority taxa) and socio-economic cost (relative profit foregone). Our results show that fishery closures in January–March, depth limits at <100 m, hook limits at <500 hooks, and gear restrictions on bottom longlines could have the greatest relative conservation impact for lowest profit foregone. However, there are clear trade-offs between taxa, with these measures primarily benefiting Critically Endangered bottlenose wedgefish (Rhynchobatus Australiae) and scalloped hammerheads (Sphyrna lewini), while potentially increasing pressure on Vulnerable silky sharks (Carcharhinus falciformis) and Endangered mako sharks (Isurus spp.). When shark fishing is important for economic welfare, and entire fishery closures or buy-outs are unfeasible, managing small-scale shark fisheries for multiple outcomes may require hard choices. This may require prioritising slow-growing Critically Endangered taxa for protection – by restricting fishing during seasons and at depths in which they are most susceptible to capture – while faster-growing taxa can continue to provide benefits for coastal communities

Status of Southeast Asia's marine sharks and rays

In Southeast Asia elasmobranchs are particularly threatened. We synthesized knowledge from the peer-reviewed and gray literature on elasmobranchs in the region, including their fisheries, status, trade, biology, and management. Our assessment included x species of sharkes and y species of rays. We found that 59% of assessed species are threatened with extinction and 72.5% are in decline; rays were more threatened than sharks. Research and conservation is complicated by the socioeconomic contexts of the countries, geopolitical issues in the South China Sea, and the overcapacity and multispecies nature of fisheries that incidentally capture elasmobranchs. The general paucity of data, funds, personnel, and enforcement hinders management. Reduced capacity in the general fishery sector and marine protected areas of sufficient size (for elasmobranchs and local enforcement capabilities) are among recommendations to strengthen conservation

Kebiasaan Makan Hiu Kejen (Carcharinus Falciformis): Studi Kasus Pendaratan Hiu Di Ppp Muncar Jawa Timur (Feeding Habit of Silky Shark (Carcharinus Falciformis): Case Study of Landing Shark in Muncar Coastal Fishing Port East Java)

Indonesia is the biggest country which produced shark in the world. Muncar Coastal Fishing Port, Banyuwangi, is a shark fishing center in East Java. Caught sharks were dominated by silky shark (Carcharinus falciformis). Primary data collected by in situ sampling and stomach content analysis. Stomach content was collected by sectio. It preserved by 10% formaline in coolbox. Silky shark had caught by shark long line and gillnet. Shark is the fish target of longline and by-catch of gillnet. Silky shark preys were grouper fish (Epinephelus sp.) as main prey and squid (Loligo sp.), beltfish (Trichiurus lepturus), sardine (Sardinella lemuru) as complementary preys. Based on stomach content analysis, silky shark was identified on 4.7 trophic level. Silky shark preys were grouper on trophic level 4.1, squid, beltfish on trophic level 4.4, sardine on trophic level 2.1. Silky shark as apex predator could be found in Bali Strait and Makassar Strait, which it classified as fertility water. The existence of silky sharks whicht prey fish in several trophic level layers made silky shark as one of the key species in Bali Strait and Makassar Strait. Catching sharks will have implications for trophic level is high or low

KEBIASAAN MAKAN HIU KEJEN (Carcharinus falciformis): STUDI KASUS PENDARATAN HIU DI PPP MUNCAR JAWA TIMUR (Feeding habit of Silky Shark (Carcharinus falciformis): Case Study of Landing Shark in Muncar Coastal Fishing Port East Java)

ABSTRACTIndonesia is the biggest country which produced shark in the world. Muncar Coastal Fishing Port, Banyuwangi, is a shark fishing center in East Java. Caught sharks were dominated by silky shark (Carcharinus falciformis). Primary data collected by in situ sampling and stomach content analysis. Stomach content was collected by sectio. It preserved by 10% formaline in coolbox. Silky shark had caught by shark long line and gillnet. Shark is the fish target of longline and by-catch of gillnet. Silky shark preys were grouper fish (Epinephelus sp.) as main prey and squid (Loligo sp.), beltfish (Trichiurus lepturus), sardine (Sardinella lemuru) as complementary preys. Based on stomach content analysis, silky shark was identified on 4.7 trophic level. Silky shark preys were grouper on trophic level 4.1, squid, beltfish on trophic level 4.4, sardine on trophic level 2.1. Silky shark as apex predator could be found in Bali Strait and Makassar Strait, which it classified as fertility water. The existence of silky sharks whicht prey fish in several trophic level layers made silky shark as one of the key species in Bali Strait and Makassar Strait. Catching sharks will have implications for trophic level is high or low.Keywords: feeding habit, silky shark, trophic level-------ABSTRAKIndonesia merupakan negara penghasil hiu terbesar di dunia. PPP Muncar, Banyuwangi merupakan salah satu pusat penangkapan hiu di Jawa Timur. Hiu yang tertangkap oleh nelayan didominasi oleh hiu kejen (Carcharinus falciformis). Data primer didapatkan dari pengambilan sampel dan analisis isi lambung. Isi lambung didapatkan dari proses pembedahan. Isi lambung diawetkan dalam formalin 10% dalam coolbox. Hiu kejen tertangkap menggunakan rawai dan gillnet. Hiu menjadi ikan target pada alat tangkap rawai dan by-catch pada gillnet. Mangsa hiu kejen adalah kerapu sebagai makanan utama dan lemuru, cumi-cumi, layur merupakan makanan pelengkap. Hiu kejen (C.falciformis) yang tertangkap di Selat Bali berada pada trofik level 4,7. Mangsa utama hiu kejen adalah kerapu (trofik level 4,1) dan mangsa pelengkap lemuru (trofik level 2,1), layur (trofik level 4,4) dan cumi-cumi. Hiu kejen sebagai salah satu apex predator dapat ditemukan di Selat Bali maupun Selat Makassar yang memiliki kesuburan tinggi. Keberadaan hiu kejen yang memangsa beberapa ikan di beberapa lapisan trofik level menjadikan hiu kejen sebagai salah satu spesies kunci di perairan Selat Bali dan Selat Makassar. Penangkapan hiu akan memberi implikasi terhadap trofik level yang tinggi maupun rendah.Kata kunci: kebiasaan makan, hiu kejen, trofik leve

KEBERLANJUTAN SUMBERDAYA IKAN KURISI (Nemipterus japonicus) DI PERAIRAN TELUK BANTEN

Ikan kurisi merupakan salah satu komoditas ikan demersal yang banyak dimanfaatkan di Perairan Teluk Banten. Tingginya pemanfaatan dapat mempengaruhi keberlanjutan sumberdaya ikan kurisi, sehingga perlunya kajian yang untuk melihat tekanan perikanan dalam runtun waktu (time series) untuk mengetahui kondisi perikanan ikan kurisi secara berkala. Metode yang digunakan adalah studi literatur menggunakan data penelitian yang telah dilakukan pada tahun 2012-2016, yang kemudian digunakan sebagai acuan dalam pembangkitan data untuk dianalisis lebih lanjut. Analisis yang dilakukan yaitu analisis pertumbuhan, spawning potential ratio dan panjang optimal pertama kali tertangkap. Hasil analisis menunjukkan bahwa ikan kurisi betina memiliki nilai parameter pertumbuhan (k) yang lebih tinggi dibandingkan jantan. Kondisi perikanan ikan kurisi yang ada di Perairan Teluk Banten tahun 2016 memiliki kondisi lebih baik dibandingkan tahun sebelumnya dengan nilai F/M = 0,73; nilai E = 0,42, nilai % immature = 11 % dan nilai SPR = 0,49 atau 49 %. Kondisi ini menunjukkan terjadi perbaikan kondisi perikanan 2012-2016 yang semula over exploited menjadi under exploited. Kata kunci:&nbsp;ikan kurisi, parameter pertumbuhan, SPR, Teluk Bante

Shark and ray monitoring on the marine critical habitat in Aceh Province

Aceh is the leading province in Indonesia, where the marine protection area for juvenile sharks and rays was first established, precisely in Aceh Jaya waters. Rigaih is the fishing port located closest to Aceh Jaya waters, where the angler fish closely with the marine protected area and even intersect with the juvenile’s habitat. This study aimed to examine shark and ray catches in Aceh Jaya before and after establishing the marine protection area. We conducted landing monitoring from 2017 to 2019 (before establishing a conservation area) and monitored in 2020 when the conservation area was established. We recorded that 73% of sharks and ray caught on set gill net. The composition of sharks and rays landed at PPI Rigaih consisted of Sphyrna lewini (75%, n=1783), Chiloscyllium punctatum (8%), Neotrygon caeruleopunctata (7%, n =175), and other species (10%). This study aimed to provide scientific recommendations to support shark conservation action in Aceh Jaya Waters. We found that Aceh Jaya waters are an important area for the life stages of several threatened species, including Scalloped Hammerhead Sharks (S.lewini) and Bottlenose Wedgefish (R.australiae) that are listed in Critically Endangered and listed in Appendix II CITES. Management to support the conservation action needs to be strengthened not only limited to Marine Protected Areas but also fisheries management to reduce the incidental catch of threatened sharks and ray species. Further studies need to be conducted to delineate the habitat range of threatened shark and ray species and identify fishing behaviours that pose a risk for incidental catches of sharks and rays

Opportunities and challenges in value chain analysis for sustainable management of sharks and rays

Studies on elasmobranch trade have often focused on a single commodity, shark fins. Such a narrow focus can result in an incomplete understanding of the socio-cultural importance of sharks, limiting discussion on the range and efficacy of potential management interventions. Assessments must be performed across the value chain from fisher to retail vendor to better conserve vulnerable elasmobranch species, offering a broader view of capture, use, and trade. Here, we collate insights from shark value chain assessments conducted in eight countries (Mexico, Peru, Guinea-Bissau, India, Bangladesh, Sri Lanka, Indonesia and Fiji) spanning five continents. Approaches and processes implemented in a shark value chain analysis (VCA) were reviewed to: (1) understand better approaches and tools and (2) collate shared experiences. Our results demonstrate that VCAs broaden the outlook of fishery and trade assessments when capturing a more comprehensive range of economic and socio-cultural aspects (e.g., livelihoods, cultural use of commodities) of trade in all shark commodities. Time invested in various components of assessments produced different outcomes, with considerable returns from stakeholder selection, survey design, and assessor/stakeholder relationship building. Contrastingly, results demonstrated that efforts in communication with stakeholder groups and policymakers could be further streamlined to focus on key results using a variety of communication formats. Outcomes from this study offer guidance to those embarking on shark VCAs, facilitating improving the assessment process and outcomes

ASPEK BIOLOGI DAN KELIMPAHAN HIU MAKO SIRIP PENDEK (Isurus oxyrinchus) DI SAMUDRA HINDIA BAGIAN TIMUR BERDASARKAN PROGRAM OBSERVER ILMIAH 2015-2019

Hiu mako sirip pendek (Isurus oxyrinchus) termasuk kedalam Famili Lamnidae dan banyak dieksploitasi sehingga telah dimasukkan ke dalam daftar merah IUCN serta Apendiks II CITES sejak 2019. Penangkapan dan perdagangannya perlu dipantau secara global untuk menghindari kepunahan. Penelitian ini bertujuan untuk mengkaji laju tangkap, kelimpahan, dan estimasi ukuran hiu mako yang tertangkap perikanan rawai tuna. Pengumpulan data dilakukan dengan menempatkan tenaga observer ilmiah diatas kapal penangkap ikan yang berbasis di empat pelabuhan utama rawai tuna pada rentang waktu tahun 2015 hingga 2019. Bobot tubuh ikan diestimasi dari ukuran panjang cagaknya berdasarkan persamaan hubungan panjang dan bobot dari penelitian-penelitian sebelumnya. Hasil penelitian mengungkap bahwa terjadi peningkatan upaya rawai tuna seiring dengan peningkatan cakupan sampling. Laju tangkap mencapai puncaknya pada tahun 2017 (0,2 ekor/1000 pancing), kemudian mengalami penurunan seiring dengan peningkatan upaya penangkapan. Secara spasial, hiu mako tersebar di wilayah perairan tropis dan subtropis, khususnya kurang dari 10o Lintang Selatan. Pertumbuhan hiu mako bersifat isometrik dengan ukuran panjang cagak berkisar antara 50-211 cm. Rata-rata ukuran hiu yang tertangkap cenderung semakin besar dari tahun ke tahun sehingga dimungkinkan memiliki implikasi pada upaya pengelolaan dan konservasinya jenis yang terancam punah ini.Shortfin mako shark (Isurus oxyrinchus) belongs to the Family Lamnidae and is widely exploited so it has been included in the IUCN red list as well as Appendix II CITES since 2019. Hence, its capture and trade need to be monitored globally to avoid extinction. This study aimed to investigate the catch rate, abundance, and size estimation of the shortfin mako shark caught by tuna longline. Data collection was conducted through the on-board scientific observer program on the fishing vessel at four main tuna longline ports during the period of 2015 to 2019. The whole-body weight was estimated by its length and weight relationship revealed from previous studies. The results showed that there was an increase in fishing efforts along with an increased sampling coverage. The catch rates peaked in 2017 (0.2 fish/1000 hooks), then, it decreased due to increased fishing efforts. Shortfin mako sharks were distributed spatially in both tropic and subtropic waters, mostly caught in area below than 10-degree South. An isometric growth was identified with the length size ranged between 50-211 cm. The average size of harvested fish tends to rise every year that may have implications to the establishment of management and conservation strategies for the endangered species