No abstract

We analyzed the variability of sea surface height anomaly (SSHA), and its relationship with Bigeye tuna catch in the eastern Indian Ocean (EIO) off of Java Island (Indonesia). Both time series of SSHA and Bigeye tuna HR show dominant signals corresponding to the annual and inter-annual variability. During the southeast monsoon the wind blows along southern coast of Java and produces coastal upwelling. This causes sea level to drop due to an offshore Ekman transport, and thermocline becomes shallower. During El Niño and Indian Ocean Dipole (IOD) positive phase, upwelling is more intense and a large cold eddy forms in the EIO off Java. Generally, Bigeye tuna HR tends to increase during upwelling seasons and becomes even higher during El Niño and the positive phase of the IOD. The increased Bigeye tuna HR during the southeast monsoon, El Niño and the IOD positive phase can be attributed to the shallower thermocline depth and the enhancement of biological productivity due to development of eddies and strong upwelling in the EIO. The spatial distribution of SSHA indicates that Bigeye tuna catches are abundant in the frontal regions between cold and warm eddies.

Status stok merupakan salah satu dasar utama dalam merumuskan pengelolaan sumber daya ikan yang berkelanjutan di WPP NRI. Tulisan ini bertujuan untuk mengevaluasi status stok sumber daya ikan di WPP NRI dan alternatf pengelolaannya. Penelitian dilaksanakan pada tahun 2015-2016 dengan menggunakan metode holistik dan analitik. Hasil analisis menunjukkan potensi sumber daya ikan di perairan Indonesia (WPP NRI) adalah sebesar 12,54 juta ton per tahun dengan potensi tertinggi sebagai ikan pelagis kecil sebesar 4,88 juta ton/tahun (39 %) dan yang terendah adalah lobster sebesar 11.159 ton (1 %). Berdasarkan WPP NRI, potensi sumber daya ikan tertinggi sebesar 2,64 juta ton (21 %) terdapat di WPP NRI 718 (Laut Aru dan Laut Arafura) dan yang terendah sebesar 425.444 ton di perairan WPP NRI 571 (Selat Malaka dan Laut Andaman). Tingkat pemanfaatan ikan di WPP NRI secara keseluruhan didominasi status fully-exploited (indikator warna kuning) sekitar 44 %, diikuti status overfishing (indikator warna merah) sekitar 38% serta status moderat sekitar 18 %. Agar sumber daya ikan di perairan WPP NRI berada dalam tahapan yang berkelanjutan, maka harus dilakukan penataan upaya penangkapan dengan mengurangi jumlah upaya penangkapan sesuai acuan upaya optimal (f.opt) pada WPP yang mengalami kondisi overfishing dan meningkatkan upaya di WPP yang tingkat pemanfaatannya masih moderat dan fully-exploited. Stock status of fish resources were a basis advices to define an apropriate fisheries management towards sustainable fish resource. The purpose of this study was to evaluate the stock status of fish resources and its management alternative in FMAs. The study was conducted from 2015 to 2016 using a holistic and analytic method. Estimation of all fish potency in Indonesia marine waters was 12.54 million tons/year which the highest potency was small pelagic fish group about 4.88 million tons/year (39 %) and the lowest potency was spiny lobster group about 11,159 tons/year (1 %). Based on the FMAs, the highest potency was about 2.64 million tons/year (21 %) in FMA 718 (Aru sea and Arafura sea) and the lowest potency was about 425,444 tons/year (3 %) found in FMA 571 (Malacca strait and Andaman sea). Most of fish resources was in the condition of fully-exploited (44 % yellow color) followed by overfishing (34 % red color) and moderate (21 % green color). Fish groups which included in the highest overfishing by FMAs were squid group. Management alternatives in those prespective are suggested to decrease the fishing effort at the level of f.opt (fishing optimum) by fish groups on the FMAs experiencing overfishing accordingly and to increase an effort at the level of f opt for fish groups on the FMAs in the fully exploited and moderate condition

Bigeye tuna is an important fish resource in the Indian Ocean. This species like other tuna species needs to be managed properly in both national and international levels. Therefore some data and information on population structure and bioreproduction are required for management purpose. The current research was conducted to identify the population structure and bioreproduction of bigeye tuna (<em>Thunnus obesus</em>) in west off Sumatera and south off Java and Nusa Tenggara of Indian Ocean where tuna fishing spots are important. This research was based on catch landed by fishermen from the Indian Ocean during 2010. Analysis of population structure was done using DNA genetic analyses and bioreproduction by using histology technique. Results show that the population structure of the bigeye tuna in the Indian Ocean consisted of two different sub populations namely sub population of west off Sumatra and sub population of south of Java and Nusa Tenggara waters. Most of catch (about 39%) was categorized as immature fish (GI I). The immature fish was mostly found in west off Sumatera waters, meanwhile the catch in south off Java and Nusa Tenggara waters was mostly categorized as mature fish. This result may indicate that south off Java and Nusa Tenggara waters is a spawning ground of the bigeye tuna.

Tujuan riset ini adalah untuk mengkaji kondisi oseanografi musiman (sebaran suhu permukaan laut, konsentrasi klorofil-a, pola arus, dan salinitas) perairan Selat Sunda secara musiman. Kajian ini menggunakan data hasil pengukuran in situ dan data penginderaan jauh multitemporal tahun 2000, 2001, 2002, dan 2004. Analisis dilakukan secara visual dan digital untuk mendapatkan gambaran dinamik mengenai kondisi oseanografi musiman perairan Selat Sunda. Hasil yang diperoleh menunjukkan bahwa nilai sebaran suhu permukaan laut Selat Sunda sepanjang tahun bervariasi, di mana nilai berkisar antara 27,0 sampai dengan 30,5°C, lebih tinggi dibanding dengan nilai sebaran hasil pengukuran in situ. Salinitas berkisar antara 31,0 sampai dengan 33,7‰ dengan nilai terendah (31,0‰) pada musim barat, sementara salinitas tertinggi (32,7 sampai dengan 33,7‰) ditemukan pada musim peralihan 2. Sebaran klorofil-a berkisar antara 0,1 sampai dengan 2,0 mg m-3. Musim barat merupakan musim dengan kandungan klorofil-a terendah 0,1 mg m-3 dan musim timur merupakan musim dengan tingkat kesuburan perairan tertinggi (1,5 sampai dengan 2,0 mg m-3). Diduga peningkatan produktivitas primer yang sangat tinggi pada musim timur selain akibat aliran massa air yang kaya nutrien dari Laut Jawa, juga akibat dari proses upwelling pada mulut selat bagian selatan. The aim of this research is to study the dynamic of the seasonal oceanography condition (sea surface temperature, chlorophyll-a concentration, sea surface height anomaly, and salinity), of the Sunda Straits waters using in situ data and satellite multitemporal images until 2000, 2001, 2002, and 2004. The oceanographic data were analyzed using visual and digital analyze to find the dynamic features. Results show that sea surface temperature was fluctuated with seasons. The values ranging from 27.0 to 30.5°C were higher than in situ measurement. The Surface salinity varied with the value of 31.0 to 33.7‰. The Lowest salinity (31.0‰) was found of the west monsoon, the highest salinity (33.7‰) at the inter monsoon 2. The Concentration of chlorophyll-a (0.1 to 2.0 mg m-3) with the highest abundance at east monsoon. The high est concentration of chlorophyll a in east monsoon may be occurred by impact of nutrient transport from Java Sea and also by contribution of upwelling process in southern mouth of Sunda Strait.