Tuna longline catch rates in the Indian Ocean: Did industrial fishing result in a 90% rapid decline in the abundance of large predatory species?

Ikan todak berparuh pendek atau ikan tumbuk atau shortbill spearfish (Tetrapturus angustirostris) merupakan salah satu hasil tangkapan sampingan rawai tuna. Informasi mengenai ikan todak berparuh pendek seperti komposisi ukuran, perbandingan kelamin, dan tingkat kematangan gonadsangat terbatas. Tulisan ini bertujuan untuk menyajikan data dan informasi mengenai aspek biologi ikan todak berparuh pendek yang merupakan hasil tangkapan sampingan dari rawai tuna yang beroperasi di Samudera Hindia. Penelitian ini dilakukan pada bulan September sampai Desember 2008 di perairan Samudera Hindia. Hasil penelitian menunjukan bahwa ikan todak berparuh pendek memiliki kisaran panjang tubuh 135-175 cmLJFL dan modus pada kisaran 155-165 cmLJFL.Perbandingan jenis kelamin ikan jantan dan betina 1:13,5, berdasarkan atas hasil uji chi-square menunjukan bahwa rasio ikan jantan dan betina pada periode penelitian ini tidak seimbang. Pada bulan September ikan todak berparuh pendek betina didominansi oleh tingkat kematangan gonad IIsebesar 66,7%, bulan Oktober oleh tingkat kematangan gonad V sebesar 46,2%, bulan Nopember oleh tingkat kematangan gonad II sebesar 53,3%, sedangkan pada bulan Desember oleh tingkat kematangan gonad III sebesar 42,9%. Pada bulan Nopember sampai Desember terlihat bahwa tingkat kematangan gonad V mulai berkurang, hal ini menunjukan bahwa pada bulan Nopember sampai Desember diduga banyak ikan todak berparuh pendek betina yang sudah memijah. Shortbill Spearfish (Tetrapturus angustirostris) is one of bycatch of tuna longline. Information about shortbill spearfish on the size composition, sex ratio, and maturity stage is still very limited. The objective this paper is to present the data and information about shortbill spearfish which is a bycatch of tuna longline that operated in the Indian Ocean. Research was conducted during September until December 2008 in Indian Ocean. The results showed that the shortbill spearfish have body length about 135-175 cmLJFL and modes in 155-165 cmLJFL. Sex ratio of the male and female was 1:13.5. Based on chi-square test showed that the ratio of male and female in the period of the study was not balanced. In September, the female stage maturity was dominated by level II of 66.7%, October by level V of 46.2%, November by level II of 53.3%, and December by level III of 42.9%. During November until December showed that the maturity stage of level V was decreased, this shows that in this time the female of shortbill spearfish was spawned.

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Distribution of Bigeye Tuna in the Indian Ocean as Seen from Tuna Longline Catches.

NIPPON SUISAN GAKKAISHI ◽

10.2331/suisan.57.1683 ◽

1991 ◽

Vol 57 (9) ◽

pp. 1683-1687

Author(s):

Masahiko Mohri ◽

Eiji Hanamoto ◽

Shoichi Takeuchi

Keyword(s):

Indian Ocean ◽

Bigeye Tuna ◽

The Indian Ocean ◽

Tuna Longline

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Bycatch and discards by Taiwanese large-scale tuna longline fleets in the Indian Ocean

Fisheries Research ◽

10.1016/j.fishres.2010.08.005 ◽

2010 ◽

Vol 106 (3) ◽

pp. 261-270 ◽

Cited By ~ 39

Author(s):

Hsiang-Wen Huang ◽

Kwang-Ming Liu

Keyword(s):

Indian Ocean ◽

Large Scale ◽

The Indian Ocean ◽

Tuna Longline

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COMPARISON OF INDONESIAN TUNA LONGLINE FISHING PERFORMANCE WITHIN AND OUTSIDE INDONESIA EXCLUSIVE ECONOMIC ZONE (EEZ)

Indonesian Fisheries Research Journal ◽

10.15578/ifrj.23.1.2017.1-6 ◽

2017 ◽

Vol 23 (1) ◽

pp. 1

Author(s):

Bram Setyadji ◽

Irwan Jatmiko

Keyword(s):

Indian Ocean ◽

Bluefin Tuna ◽

T Test ◽

Exclusive Economic Zone ◽

Southern Bluefin Tuna ◽

The Indian Ocean ◽

The Mean ◽

Economic Zone ◽

Tuna Longline ◽

High Seas

Indonesian tuna longline fleets have been fishing in the Exclusive Economic Zone (EEZ) and high seas of the Indian Ocean for quite some time. However, effort has never been made to separate catch from the EEZ and the high seas as it important for fisheries management. A total of 2,430 set-by-set longline fishing data had been collected by scientific observers based in the Research Institute of Tuna Fishery in Bali since August 2005 to December 2014 on which present analysis was made. The research aims to compare between trend of tuna catch of the EEZ and of the high seas of Indian Ocean. The results show that the mean hook rate of both catches of big eye tuna (BET) and southern Bluefin tuna (SBT) caught in the high seas was significantly higher than that the EEZ (two sample t-test, p<0.05), while for yellow fin tuna (YFT) it was in the opposite direction (two sample t-test, p<0.05). As for albacore (ALB), the mean hook rate value was statistically similar in both fishing grounds (two sample t-test, p>0.05).

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Stock depletion of yellowfin tuna Thunnus albacares (Bonnaterre 1788) in the Northeastern Indian Ocean

E3S Web of Conferences ◽

10.1051/e3sconf/202132205004 ◽

2021 ◽

Vol 322 ◽

pp. 05004

Author(s):

Bram Setyadji ◽

Hety Hartaty ◽

Arief Wujdi ◽

Ririk K. Sulistyaningsih

Keyword(s):

Indian Ocean ◽

Data Collection ◽

Relative Abundance ◽

Yellowfin Tuna ◽

Coastal Communities ◽

Thunnus Albacares ◽

The Indian Ocean ◽

Stock Depletion ◽

Longline Fisheries ◽

Tuna Longline

The stock of yellowfin tuna (Thunnus albacares) has been in a declining trend in the last five years. Although the noticeable decline mainly occurred in the western part of the Indian Ocean, uncertainty lingers on how this phenomenon will affect the opposite leg. The study aimed to investigate the dynamics of stock through monitoring several indicators by utilizing logbooks, scientific port sampling, and observer data available. The result showed that both relative abundance and estimated catch trend are declining in recent years, a sign that the negative global inclination also influences Indonesian tuna longline fisheries. Further studies are needed to understand whether this phenomenon also impacts other gears. Hence, mitigation on conserving the resource by reducing the catch and strengthening the data collection should be the priority to maintain the livelihood and welfare of many coastal communities.

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KEDALAMAN RENANG DAN WAKTU MAKAN IKAN ALBAKORA (Thunnus alalunga) DI SAMUDERA HINDIA SEBELAH SELATAN JAWA

BAWAL Widya Riset Perikanan Tangkap ◽

10.15578/bawal.6.2.2014.89-94 ◽

2015 ◽

Vol 6 (2) ◽

pp. 89

Author(s):

Andi Bahtiar ◽

Abram Barata ◽

Budi Nugraha

Keyword(s):

Surface Layer ◽

Indian Ocean ◽

Feeding Periodicity ◽

The Indian Ocean ◽

Thunnus Alalunga ◽

Tuna Longline

Albakora adalah salah satu spesies tuna yang berupa hasil tangkapan beku bernilai ekonomis tinggi bagi kapal-kapal rawai tuna. Penangkapan albakora di Samudera Hindia semakin kompetitif, sehingga setiap nahkoda dan nelayan kapal rawai tuna perlu memiliki pengetahuanmengenai tingkah laku ikan seperti kedalaman renang dan waktu makan. Penelitian ini dilakukan dengan metode observasi langsung di atas kapal rawai tuna yang berbasis di Benoa dan Palabuhanratu sebanyak 3 trip mulaiMaret sampai Nopember 2013. Tujuan penelitian ini adalah untuk mengetahui kedalaman renang dan waktu makan albakora di Samudera Hindia. Hasil penelitian menunjukkan bahwa kedalaman renang albakora berdasarkan pengamatan data minilogger berada pada kisaran 57,04 - 325,46 m. Albakora lebih banyak tertangkap pada lapisan renang permukaan hingga pertengahan. Intensitas kebiasaan albakora mencarimakanan dilakukan antara pukul 07:45 - 17:59, dengan frekuensi tertinggi aktifmakan yaitu pada selang pukul 10:00 - 11:00. Untukmendapatkan hasil tangkapan albakora yang berlimpah, maka nelayan rawai tuna perlumenggunakanmetode penangkapan dengan perpaduan tipe rawai tuna permukaan dan pertengahan. Pengaturan waktu setting yang dimulai pagi hari dan waktu hauling mulai sore hari adalah waktu yang ideal dalampenangkapan albakora di Samudera Hindia.Albacore is one of the tuna species and mostly landed as frozen catch on tuna longliner. Albacore fishing in Indian Ocean more competitive, so Fishermans or Fishing Masters of tuna longliner must have knowledge of tuna behavior such as swimming layer and feeding periodicity. Research was conducted with observation on board on tuna longliner based Benoa and Palabuhanratu, totally 3 trips during March until November 2013. The aim of research are to know of swimming layer and feeding periodicity of albacore in Indian Ocean. Theresults showed that the swimming layer of albacore based minilogger data are distributed at 57.04 to 325.46 m The results showed that the swimming layer of albacore at 57.04 to 325.46 m. Albacore mostly catched in surface layer to middle in Indian Ocean. The feeding periodicity of albacore’s are start from 7:45pm to 17:59pm, mostly active at 10pmto 11pm. For the maximum catch of albacore’s, every fisherman of tuna longline must have a good fishing tactics. The combination of surface and middle tuna longline types are the best fishing tactics to be applied. The setting of tuna longline begin morning and hauling begin afternoon are the best time for fishing of albacore in the Indian Ocean.

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DISCARDS OF THE INDONESIAN TUNA LONGLINE FISHERY IN INDIAN OCEAN

Indonesian Fisheries Research Journal ◽

10.15578/ifrj.19.1.2013.25-32 ◽

2013 ◽

Vol 19 (1) ◽

pp. 25

Author(s):

Bram Setyadji ◽

Budi Nugraha

Keyword(s):

Indian Ocean ◽

Longline Fishery ◽

Total Catch ◽

The Indian Ocean ◽

By Catch ◽

Tuna Longline

Incidental by-catch and associated discarding are difficult to estimate on the basis of logbook information because they are poorly reported by fishing masters and their importance varies with several interrelated factors. The purpose of this paper is to inform the commonly discarded fishes of the Indonesian tuna longline fishery in the Indian Ocean. The study was carried out during 2010 – 2011 following six commercial tuna longline vessels based in Port of Benoa. Discards composition was dominated by longnose lancetfish and pelagic stingrays which composed almost half of total discards. Almost half of total catch are discards and half of discards are disposed dead or dying.

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