DINAMIKA SPASIAL IKAN MESOPELAGIS (ceratoscopelus warmingii LÜTKEN, 1892) DI SAMUDERA HINDIA

Abstract

Kajian mengenai ikan mesopelagis di perairan Samudera Hindia masih sangat terbatas, sehingga informasi terkait kelimpahan jenis ikan mesopelagis di Samudera Hindia sangat penting. Survei trawl lapisan pertengahan dilakukan pada tanggal 26 Juni-16 Juli 2015 di perairan laut lepas (high seas) Samudera Hindia untuk memperoleh data dan informasi tersebut dengan menggunakan kapal penelitian R.V. Dr. Fridtjof Nansen. Hasil penelitian menunjukkan distribusi kedalaman vertikal di malam hari jenis yang dominan C.warmingii sesuai dengan kedalaman operasi trawl yaitu 86,9 ± 38,6 m. Namun pada siang hari tidak ditemukan spesies C. warmingii saat operasi trawl pada kedalaman rata-rata 444,3 ± 45,96 m. Diperkirakan ketika siang hari distribusi C. warmingii terkonsentrasi pada lapisan perairan lebih dalam sehingga tidak terjangkau oleh jaring trawl tersebut. Distribusi spasial secara horizontal pada malam hari menunjukkan pola konsentrasi tertinggi berada pada area gyre yang diindikasikan dengan pola geostrophic circulation. Sementara, prosentase C. warmingii yang merupakan hasil tangkapan seluruh stasiun trawl selama penelitian terdiri dari 2,58% fase larva, 27,21% juvenile, dan 60,21% dalam keadaan dewasa.Studies on mesopelagic fishes in the Indian Ocean are relatively limited, therefore data and information regarding spatial dynamic of the most abundant mesopelagic fish species Ceratoscopelus warmingii in the Indian Ocean would contribute a significant information on deepsea marine biodiversity. Pelagic-trawl stations were used to collect and identify the spatial dynamic of C. warmingii in the main scattering layers of the water column. Survey were carried out by RV Dr. Fridtjof Nansen in the high seas of Indian Ocean. Observation were made during day and night on 26th June to 16th July 2015 as part of the second International Indian Ocean Expedition (IIOE 2). The result shows that vertical distributions of C. warmingii were concentrated at the average depth 86.9 ± 38.6 m during nighttime. There were no individuals found during the daytime at the average depth 444.3 ± 45.96 m, diurnal migrations of C. warmingii  to more than the depth of trawl operation might explain the absent of this species. Horizontal spatial distribution of trawl catches (number per hour) during nighttime show high concentration of C. warmingii close to gyre indicated by geostrophic circulation. Moreover, the total catches of C. warmingii across the Indian Ocean are dominated by 60.21% adult, 27.21% juvenile, and 2.58% larvae, respectively.