SEBARAN UNIT STOK IKAN LAYANG (Decapterus spp.) DAN RISIKO PENGELOLAAN IKAN PELAGIS KECIL DI LAUT JAWA

Abstract

Ikan layang (Decapterus russelli dan D. macrosoma, Fam. CARANGIDAE) merupakan komponen utama dari sumberdaya ikan pelagis kecil di perairan sekitar Laut Jawa-Selat Makassar. Peningkatan upaya secara tak terkontrol pada perikanan purse seine telah mengakibatkan penyusutan biomassa yang berdampak pada penurunan hasil tangkapan, sehingga tujuan pengelolaan yang berkelanjutan tak tercapai; ditambah lagi pengetahuan tentang karakter biologi dan keterkaitan diantara stok di sekitar zona utama belum diketahui secara jelas. Paper ini membahas dugaan sebaran stok dan risiko pengelolaannya berdasarkan data penstrukturan populasi dua species ikan layang (D. russelli dan D. macrosoma) dan aspek perikanan tangkap (komposisi jenis, sebaran fishing ground). Data struktur populasi diperoleh dari hasil analisis genetik terhadap marker DNA mitochondria (metode RFLP) yang telah dilaporkan sebelumnya; sedang data aspek penangkapan diperoleh dari tempat pendaratan utama di Pekalongan, Samarinda, Mamuju dan sekitarnya. Hasil menunjukkan kedua species layang memiliki masing-masing dua sub populasi (2 unit stok). D. russelli, tersebar di Laut Jawa bagian timur, Laut Flores bagian selatan dan Laut Banda bagian barat (sub populasi atau unit stok 1), sedang unit stok 2 tersebar di Selat Makassar laut dangkal di timur Kalimantan. Sedangkan pada D. macrosoma, unit stok Laut Banda (unit stok 1) terpisah (berbeda) dengan unit stok lain yang tersebar di Laut Flores zona pantai, Laut Jawa bagian timur dan Selat Makassar laut dangkal. Dari hal tersebut pengelolaan ikan pelagis kecil di Laut Jawa (WPP 712) dan Selat Makasar laut dangkal (WPP 713) sebaiknya disatukan sebagai satu unit stok dan satu unit managemen. Di pihak lain, perikanan pelagis di Selat Makasar laut dalam di perairan barat Sulawesi disarankan dikelola dalam konteks penstrukturan populasi ikan pelagis kecil laut
dalam di sekitar Sulawesi (malalugis, D. macarellus). Pola migrasi ikan layang/pelagis dalam arah Laut Jawa – Selat Makasar dan sebaliknya dimungkinkan juga terkait dengan penstrukturan populasi layang tersebut.

Layang scad (Decapterus russelli) and round scad (D. macrosoma) was a main component of small pelagic fishes around Java Sea-Makasar Strait. Increasing of uncontrolled effort of purse seine had caused a biomass decrease and clearly impact to the lower catch, so that a goal of sustainable fishery was difficult to reach; in addition, knowledge on biological characteristics and inter-relationship within the stock unit in the main zone was not understood yet. Study on stock distribution and its management impacts was conducted based on the population structuring of the two scads species exist (D. russelli and D. macrosoma) which was observed fromthe genetic analyses of the mitochondria DNA marker (RFLP method), and the capture fishery data (species composition, distribution of fishing ground) from some main landing sites such as Pekalongan, Samarinda, Mamuju, and Bone. Results showed the two species of scads had two sub population (stock unit) respectively. D. russelli distribute in the eastern part of Java Sea, southern Flores Sea, and western Banda Sea exist as a sub population or stock unit 1, while a stock unit 2 was distributed around the coastal waters of Makasar Strait in eastern Kalimantan. However, stock unit 1 of D. macrosoma that distribute in Banda Sea was separated (clearly different) from the stock unit 2 that was distributed in the coastal habitat of Flores Sea, eastern Java Sea, and the coastal area of Makasar Strait (east Kalimantan). Thus, a sustainable management of small pelagic fish in the areas of Java Sea (FMA 712) and Makasar Strait (FMA 713) have to be managed as a one stock unit (sub population) and one management unit. On the other hand, we would like to propose that for a small pelagic fish that was distributed in the oceanic habitat of Makasar Strait (western Sulawesi) should be managed in the context of population structuring of scad mackerel/malalugis (D. macarellus) as the main oceanic species of small pelagic fish around Sulawesi. Migration pattern of that two scads (D. russelli and D. macrosoma) along the Java Sea and Makasar Strait and vise versa may be related to that proposed population structuring of scads.