Modelling the effect of marine protected areas on the population of skipjack tuna in the Indian Ocean

Abstract In recent years, the international community has become increasingly aware of the growing threats to marine biodiversity in areas beyond national jurisdiction (abnj), and international discussions on a new international legally binding are underway. In parallel, some States, through regional organisations, have progressively extended their activities into abnj, particularly through the development of area-based management tools (abmts). In this article, we consider how actors in the Western Indian Ocean (wio) might engage in abnj governance. In particular, we develop some possible scenarios for developing abmts in the wio, including through the development of fisheries closures, the establishment of marine protected areas (mpas), and the adoption of abmts under the auspices of relevant international organisations. We conclude that while the wio is currently not the most advanced region in terms of ongoing efforts to improve the governance of abnj, there are already some positive signals and promising options for the future.

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PENENTUAN UKURAN PERTAMA KALI MATANG GONAD (Lm) CAKALANG (Katsuwonus pelamis Linnaeus, 1758) DI SAMUDRA HINDIA SELATAN BALI

Jurnal Penelitian Perikanan Indonesia ◽

10.15578/jppi.25.2.2019.135-145 ◽

2019 ◽

Vol 25 (2) ◽

pp. 135

Author(s):

Hety Hartaty ◽

Gussasta Levi Arnenda

Keyword(s):

Indian Ocean ◽

Oocyte Development ◽

Oocyte Diameter ◽

Skipjack Tuna ◽

Katsuwonus Pelamis ◽

Multiple Spawner ◽

The Indian Ocean ◽

First Maturity ◽

Paraffin Method ◽

Immature Fish

Cakalang tergolong kelompok jenis ikan pelagis besar yang keberadaanya cukup melimpah di perairan Samudera Hindia termasuk perairan selatan Bali. Informasi biologi reproduksi sangat penting terutama untuk mengetahui kapan ikan tersebut memijah sehingga dapat digunakan sebagai dasar pengelolaannya. Cakalang memijah beberapa kali (multiple spawner), hal ini diketahui berdasarkan tingkat perkembangan oosit yang lebih dari satu tingkatan dalam satu gonad aktif. Sampel gonad cakalang betina diperoleh dari Pangkalan Pendaratan Ikan Kedonganan, Bali. Sebanyak 106 ekor cakalang betina dengan kisaran panjang cagak 37-71 cmFL dan kisaran bobot 902-7.214 gram yang teramati. Sampel gonad dalam keadaan segar langsung difiksasi menggunakan larutan buffer-formalin 10% kemudian dianalisis secara histologis menggunakan metode parafin dan pewarnaan HE (Harris-Haemotoxilin dan Eosin). Cakalang betina yang diklasifikasikan sebagai ikan yang belum dewasa (immature) memiliki karakteristik oosit unyolked (UY) yang lebih gelap pewarnaannya, memiliki diameter <156 µm dan Early yolked (EY) yang memiliki diameter 114-249 µm. Cakalang dewasa (mature) memiliki karakteristik perkembangan ovari berupa adanya oosit pada tingkat yang lebih tinggi yaitu advanced yolked (AY) dengan diameter oosit berkisar antara 180-448 µm, migratory nucleus (MN) 239-468 µm dan hydrated (Hy) dimana ukuran oositnya sangat besar yaitu sekitar 459-552 µm dan berbentuk seperti noda merah muda (pink stain). Cakalang betina di perairan Samudera Hindia selatan Bali memiliki perkembangan oosit yang asynchronous (tidak seragam) yang ditandai oleh munculnya beberapa tingkat perkembangan oosit dalam satu ovari. Ukuran panjang pertama kali matang gonad (Lm) cakalang betina yaitu 44,7 cmFL. Cakalang betina dewasa yang berstatus memijah aktif (actively spawning) ditemukan di setiap bulan pengamatan (April-September) dan diduga memijah sepanjang tahun. Skipjack tuna is classified as a large pelagic fish species and has abundant presence in the waters of the Indian Ocean including the waters of southern Bali. Information related to reproductive biology is very important especially to find out when the fish spawn so that they can be used as a basis for its management. Skipjack spawns several times (multiple spawner), this is known based on the level of oocyte development that was more than one level in one active gonad. Samples of female skipjack gonads were obtained from Kedonganan, Bali. A total of 106 female skipjack tuna with length range of 37-71 cmFL and weight range of 902-7,214 grams were observed. Gonad samples in fresh condition were immediately fixed using a 10% buffer-formalin solution then histologically analyzed using the paraffin method and HE staining (Harris-Haemotoxilin and Eosin). Female skipjack classified as immature fish has the characteristics of unyolked oocytes (UY) which are darker in coloration, have a diameter <156 ìm and Early yolked (EY) which has a diameter of 114-249 ìm. Adult skipjack (mature) has the characteristics of ovarian development in the form of oocytes at a higher level, namely advanced yolked (AY) with oocyte diameter ranging from 180-448 µm, migratory nucleus (MN) 239-468 µm and hydrated (Hy) where oocyte size is very large, which is around 459-552 µm and shaped like a pink stain. Female skipjack in the waters of the Indian Ocean south of Bali has an asynchronous (non-uniform) oocyte development which is characterized by the appearance of several levels of oocyte development in one ovary. Size at first maturity (Lm) of female skipjack in Indian Ocean southern Bali was 44.7 cmFL. Adult skipjack females with active spawning status are found every month of observation (April-September) and suspected to spawn throughout the year.

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PERIKANAN TUNA SIRIP KUNING (Thunnus albacares Bonnaterre, 1788) PADA ARMADA TONDA DI SAMUDERA HINDIA SELATAN JAWA

BAWAL Widya Riset Perikanan Tangkap ◽

10.15578/bawal.11.3.2019.161-173 ◽

2019 ◽

Vol 11 (3) ◽

pp. 161

Author(s):

Maya Agustina ◽

Bram Setyadji ◽

Prawira Atmaja Rintar Pandapotan Tampubolon

Keyword(s):

Indian Ocean ◽

Size Structure ◽

Landing Site ◽

Yellowfin Tuna ◽

Fishing Gear ◽

Thunnus Albacares ◽

Skipjack Tuna ◽

The Indian Ocean ◽

Average Size ◽

Relationship Of

Tuna sirip kuning (Thunnus albacares) merupakan hasil tangkapan terbanyak dibandingkan dengan jenis tuna lainnya di Indonesia. Ketersediaan stok tuna sirip kuning di Samudra Hindia, pada saat ini, diperkirakan dalam keadaan lebih tangkap. Oleh karena itu, pengelolaan secara tepat dan bertanggungjawab penting dilakukan untuk melindungi spesies tuna, salah satu caranya dengan mengkaji alat tangkap yang digunakan. Tulisan ini bertujuan untuk mengungkapkan produktivitas dan hasil tangkapan armada tonda, serta struktur ukuran dan hubungan panjang bobot ikan tuna sirip kuning yang di daratkan di selatan Jawa. Komposisi tangkapan tertinggi dari armada tonda diseluruh pendaratan ikan tuna di selatan Jawa terdiri atas tuna sirip kuning dan cakalang. Analisis CPUE menunjukkan hasil yang fluktuatif di setiap lokasi pendaratan tuna sirip kuning di Selatan Jawa. Tuna sirip kuning yang tertangkap di selatan Jawa dengan armada tonda sebagian besar adalah ikan yang belum layak tangkap karena berukuran kurang dari 100 cmFL. Struktur ukuran panjang tuna sirip kuning yang tertangkap semakin ke Timur semakin panjang ukurannya. Pola pertumbuhan tuna sirip kuning yang tertangkap di Binuangeun memiliki pola isometrik, PPN Palabuhanratu bersifat allometrik Positif, PPP Sadeng, P2SKP Pacitan, PPN Prigi dan P2SKP Sendang Biru bersifat allometrik negatif. Yellowfin tuna (Thunnus albacares) is the largest catch compared to other tuna species in Indonesia. The availability of yellowfin tuna stock in the Indian Ocean, at present, is estimated to be in overfished condition. Therefore, proper and responsible management is important to protect the species. One of the ways is by studying the used fishing gear. This paper aims at determining vessel’s productivity, as well as composition, size structure and length-weight relationship of yellowfin tuna catches from troll line fleet in the Indian Ocean part of south Java. The highest catch of tuna in all of the troll line landing places was yellowfin tuna, following by skipjack tuna. CPUE analysis showed fluctuating results at each landing site. Yellowfin tuna sizes caught by troll line fleet were mostly less than 100 cmFL and categorized as should not be properly caught. Geographically, getting to the east the average size of the catches tend to be larger. The growth pattern of yellowfin tuna catches landed in Binuangeun was isometric; Palabuhanratu was positive allometric; while those landed in Sadeng, Pacitan, Prigi and Sendang Biru were negative allometric.

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Tracking seabirds to identify potential Marine Protected Areas in the tropical western Indian Ocean

Biological Conservation ◽

10.1016/j.biocon.2011.11.015 ◽

2012 ◽

Vol 156 ◽

pp. 83-93 ◽

Cited By ~ 54

Author(s):

Matthieu Le Corre ◽

Audrey Jaeger ◽

Patrick Pinet ◽

Michelle A. Kappes ◽

Henri Weimerskirch ◽

...

Keyword(s):

Indian Ocean ◽

Protected Areas ◽

Marine Protected Areas ◽

Western Indian Ocean

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BIOLOGI REPRODUKSI IKAN CAKALANG (Katsuwonus pelamis) DI SAMUDERA HINDIA BAGIAN TIMUR

BAWAL Widya Riset Perikanan Tangkap ◽

10.15578/bawal.7.2.2015.87-94 ◽

2015 ◽

Vol 7 (2) ◽

pp. 87

Author(s):

Irwan Jatmiko ◽

Hety Hartaty ◽

Andi Bahtiar

Keyword(s):

Indian Ocean ◽

Histological Analysis ◽

Gonadosomatic Index ◽

Fork Length ◽

Maturity Stage ◽

Skipjack Tuna ◽

Katsuwonus Pelamis ◽

The Indian Ocean ◽

The One ◽

First Maturity

Cakalang (Katsuwonus pelamis) adalah salah satu hasil tangkapan penting bagi nelayan di Samudera Hindia. Penelitian ini bertujuan untuk mengetahui perkembangan gonad dan panjang pertama kalimatang gonad cakalang di Samudera Hindia. Sampel cakalang dikumpulkan dari beberapa tempat di Pantai Selatan Jawa yaitu: Palabuhanratu, Cilacap, Pacitan, Sendang Biru, Kedonganan, Tanjung Luar, Labuhan Lombok dan Oeba dari bulan April 2012 sampai November 2013. Panjang cagak dari 136 sampel berkisar antara 35-68 cm. Tingkat kematangan gonad (TKG) diamati secara histologi dan analisis Gonadosomatic index (GSI). Hasil penelitian ini menunjukkan bahwa TKGcakalang didominasi oleh TKGIV sebesar 43%, diikuti dengan TKG III (21%), TKG I (17%), TKG II (16%) dan TKG V (2%). Panjang pertama kali matang gonad terjadi pada ukuran 42,9 cm. Skipjack tuna (Katsuwonus pelamis) is the one of the important catch for fishermen in the Indian Ocean. The objectives of this research are to investigate gonad maturity and length at first maturity for female cakalang in Indian Ocean. Skipjack tuna were sampled from several places in South Coast of Java i.e.: Palabuhanratu, Cilacap, Pacitan, Sendang Biru, Kedonganan, Tanjung Luar, Labuhan Lombok and Oeba from April 2012 to November 2013. Fork length of the sampled 136 fish ranged from 35 to 68 cm.Maturity stage (TKG) investigate using histological analysis and Gonadosomatic index (GSI) calculation. The results showed that maturity stage of skipjacktuna dominated by TKG IV with 43%, followed by TKG III (21%), TKG I (17%), TKG II (16%) dan TKG V (2%). Length at first maturity occurred at 42.9 cm.

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Modelling the skipjack tuna dynamics in the Indian Ocean with APECOSM-E – Part 2: Parameter estimation and sensitivity analysis

Ecological Modelling ◽

10.1016/j.ecolmodel.2012.02.008 ◽

2012 ◽

Vol 245 ◽

pp. 55-64 ◽

Cited By ~ 16

Author(s):

Sibylle Dueri ◽

Blaise Faugeras ◽

Olivier Maury

Keyword(s):

Sensitivity Analysis ◽

Parameter Estimation ◽

Indian Ocean ◽

Skipjack Tuna ◽

The Indian Ocean

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Post-2020 Kunming 30% target can easily protect all endemic sharks and rays in the Western Indian Ocean and more

10.1101/2021.03.08.434293 ◽

2021 ◽

Author(s):

Jessica Cheok ◽

Rima W. Jabado ◽

David A. Ebert ◽

Nicholas K. Dulvy

Keyword(s):

Indian Ocean ◽

Protected Areas ◽

Marine Protected Areas ◽

Regional Cooperation ◽

Western Indian Ocean ◽

Marine Biodiversity ◽

Conservation Priorities ◽

Management Actions ◽

Regional Collaboration ◽

Distribution Ranges

SummarySharks and rays are possibly the most threatened Class of marine fishes and their declines can be halted if protected areas are optimised to benefit these species. We identify spatial priorities for all 63 endemic sharks and rays in the marine biodiversity hotspot, the Western Indian Ocean (WIO). Collectively, while the WIO nations currently surpass the 10% Aichi ocean protection target, this amounts to a dismal protection of only 1.57% of each species’ distribution range. We show that the entire ranges of all endemics can be achieved by protecting 11% of EEZs of WIO nations, well within reach of the new 30% of oceans by 2030 target. Regional management bodies exist, which if taken advantage of to implement shark and ray management, provide opportunities to implement more efficient management across the region. We recommend key management actions to implement and explicit incentivisation of international cooperation in the post-2020 biodiversity framework.Science for SocietyThe past decade has seen massive growth in the establishment of marine protected areas (MPAs), driven by the Aichi biodiversity target of protecting 10% of all ocean areas. This expansion of MPAs, however, has largely occurred in areas residual to extractive uses, often coinciding with less threatened areas of lower conservation value. This coming decade will see a further push to ensure 30% of the oceans are protected by 2030. It is important to understand how existing and future MPAs should be placed to benefit threatened biodiversity. Currently this is unclear for sharks and rays, comprising a species group that is the most evolutionarily distinct vertebrate radiation in the world and also one of the most threatened. We identify both regional and national conservation priorities for expanding marine protected areas to benefit all 63 endemic sharks and rays occurring in the Western Indian Ocean region. We find that the region has already exceeded the 10% ocean protection target, but this amounts to an average of only 1.57% protection of the distribution ranges of these species. We show that protecting the top 10% priority sites will conserve almost half of the geographic range of each species yet require only 1.16% of the total EEZ – a tiny fraction of the 30% by 2030 target. We also show that regional collaboration among all nations can result in more spatially efficient conservation priorities. We recommend that the post-2020 biodiversity framework needs to explicitly incentivise regional cooperation between nations to efficiently achieve urgent targets and maximise benefits to biodiversity.

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Variability in reproductive investment of skipjack tuna (Katsuwonus pelamis) in relation to the ocean - climate dynamics in the tropical eastern Indian Ocean

Marine and Freshwater Research ◽

10.1071/mf11146 ◽

2012 ◽

Vol 63 (8) ◽

pp. 695 ◽

Cited By ~ 3

Author(s):

Yu Kanaji ◽

Toshiyuki Tanabe ◽

Hikaru Watanabe ◽

Tatsuki Oshima ◽

Makoto Okazaki

Keyword(s):

Indian Ocean ◽

Gonadosomatic Index ◽

Subsurface Layer ◽

Austral Summer ◽

Eastern Indian Ocean ◽

Skipjack Tuna ◽

Katsuwonus Pelamis ◽

Allocation Pattern ◽

Ocean Climate ◽

The Indian Ocean

The Indian Ocean is characterised by significant climatic and oceanographic variability such as the seasonal monsoon and the decadal and inter-annual oscillation of the Indian Ocean Dipole (IOD). Understanding the effects of ocean–climate variability on marine top predators is important for both fisheries and ecosystem management. To test the hypothesis that variability in surface and subsurface temperature affects the annual reproductive cycles of skipjack tuna (Katsuwonus pelamis) in the tropical eastern Indian Ocean, we examined the seasonal and inter-annual variations of the gonadosomatic index (GSI) and determined hatch date by using otolith microstructure analysis. The GSI tended to be higher in January–February during the north-eastern monsoon when seawater cooling at the subsurface layer is induced by the seasonal inflow of the South Equatorial Countercurrent (SECC). The mode of the hatch-month distribution was also detected in that season. The generalised linear model (GLM) resulted in a dome-shaped quadratic relationship, with a peak GSI between 24°C and 26°C occurring at a depth of 50 m during austral summer. These findings indicate that seasonal monsoons and associated changes in oceanographic conditions strongly affect the energy-allocation pattern of skipjack tunas.

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Otolith chemical fingerprints of skipjack tuna (Katsuwonus pelamis) in the Indian Ocean: First insights into stock structure delineation

PLoS ONE ◽

10.1371/journal.pone.0249327 ◽

2021 ◽

Vol 16 (3) ◽

pp. e0249327

Author(s):

Iraide Artetxe-Arrate ◽

Igaratza Fraile ◽

Jessica Farley ◽

Audrey M. Darnaude ◽

Naomi Clear ◽

...

Keyword(s):

Chemical Composition ◽

Indian Ocean ◽

Equatorial Indian Ocean ◽

Otolith Microchemistry ◽

Stock Structure ◽

Skipjack Tuna ◽

Katsuwonus Pelamis ◽

Nursery Areas ◽

Chemical Signatures ◽

The Indian Ocean

The chemical composition of otoliths (earbones) can provide valuable information about stock structure and connectivity patterns among marine fish. For that, chemical signatures must be sufficiently distinct to allow accurate classification of an unknown fish to their area of origin. Here we have examined the suitability of otolith microchemistry as a tool to better understand the spatial dynamics of skipjack tuna (Katsuwonus pelamis), a highly valuable commercial species for which uncertainties remain regarding its stock structure in the Indian Ocean. For this aim, we have compared the early life otolith chemical composition of young-of-the-year (<6 months) skipjack tuna captured from the three main nursery areas of the equatorial Indian Ocean (West, Central and East). Elemental (Li:Ca, Sr:Ca, Ba:Ca, Mg:Ca and Mn:Ca) and stable isotopic (δ13C, δ18O) signatures were used, from individuals captured in 2018 and 2019. Otolith Sr:Ca, Ba:Ca, Mg:Ca and δ18O significantly differed among fish from different nurseries, but, in general, the chemical signatures of the three nursery areas largely overlapped. Multivariate analyses of otolith chemical signatures revealed low geographic separation among Central and Eastern nurseries, achieving a maximum overall random forest cross validated classification success of 51%. Cohort effect on otolith trace element signatures was also detected, indicating that variations in chemical signatures associated with seasonal changes in oceanographic conditions must be well understood, particularly for species with several reproductive peaks throughout the year. Otolith microchemistry in conjunction with other techniques (e.g., genetics, particle tracking) should be further investigated to resolve skipjack stock structure, which will ultimately contribute to the sustainable management of this stock in the Indian Ocean.

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