Kajian perikanan trawl demersal: evaluasi tiga jenis Bycatch Reduction Device (BRD)

Abstract

In recent years, global concern over the impacts of fishing activity on non-target species termed as “by-catch” has been increasing. Most of conventional shrimp trawls are poorly selective so they retain large quantities of bycatch (Saila 1983). The main objective of this research is to determine the type of bycatch reduction device which is appropriate for demersal trawl in Indonesia. This was achieved by three following objectives : 1) to compare the effectiveness three BRDs in reducing the bycatch from the industrial trawl fisheries, 2) to observe the process escapement of fish from three types of bycatch reduction device, and 3) to analyze characteristic of the bycatch from small scale demersal trawl fisheries. There were three types of BRDs tested for this study, i.e. the TED super shooter BRD, the square mesh window BRD, and the fish eye BRD. The TED super shooter BRD reduced reduced the compressed fish down to 4,98% and the anguilliform fish down to 0,47%, the square mesh window reduced the compressed fish down to 6,23% and the fish eye reduced the compressed fish down to 10,23% and the anguilliform fish down to 4,62%. Observation in the flume tank revealed that the BRD super shooter reduce compressed fish up to 30% and depressed fish 30%. The square mesh window reduced the compressed fish up to 50% and depressed fish 50%. While the fish eye BRD reduce compressed fish 30% and depressed fish 50%. The bycatch and target catch from 30 fishing trip in Blanakan in July 2007 were 52,92 kg and 354,88 kg (ratio of 1:6) and in December 2007 were 192 kg and 788 kg (ratio of 1:4). The bycatch and target catch from 30 fishing trip in Eretan Kulon in July 2007 were 101,38 kg and 273,43 kg (ratio of 1:3) and in December were 194,2 kg and 692 kg (ratio of 1:4). The bycath from Blanakan was dominated by compressed fish such as Leiognathidae, Sciaenidae, Nemipteridae and Mullidae, depressed fish from Platychepalidae. The composition of the bycatch from Eretan Kulon were dominated by compressed fish such as Sciaenidae, Leiognathidae, Nemipteridae and Mullidae, fusiform fish from Synodontidae. Since the bycatch was dominated by compressed fish, then bycatch reduction device fish eye and square mesh window are recommended to be used in Indonesian trawl fisheries.

spesies ikan atau hewn air lainnya menjadi masalah besar ketika bycatch yang dikembalikan kelaut (discarded) tidak semuanya dalam keadaan hidup atau berpeluang baik untuk hidup. Pada perikanan trawl demersal masalah ini muncul karena alat tangkap trawl tidak selektif dalam menangkap ikan dan bycatch yang tertangkap umumnya berukuran kecil atau masih dalam tingkat pertumbuhan juvenil. Trawl umumnya mempunyai selektivitas yang rendah karena ukuran mata jaring pada bagian kantong (codend) biasanya kecil menyebabkan ikan yang berukuran kecil ikut tertangkap. Untuk itu perlu dilakukan upaya untuk mengurangi hasil tangkapan sampingan sehingga keberlanjutan dari sumberdaya ikan demersal dapat terus terjaga. Hal ini sejalan dengan yang telah dicanangkan oleh FAO (1995) dalam Code of Conduct for Responsible Fisheries menyebutkan “state(s) and users of aquatic ecosystems should minimize waste, catch of nontarget species, both fish and non-fish species, and impacts on associated or dependent species”. Salah satu upaya yang dilakukan untuk merespon yang telah dicanangkan dalam FAO (1995), yaitu dengan meningkatkan selektivitas alat tangkap trawl dasar untuk mengurangi masalah hasil tangkap sampingan (bycatch) khususnya perikanan trawl udang (Brewer et al., 1998, Broadhurst dan Kennelly, 1996). Peningkatan selektivitas trawl udang telah banyak diterapkan di beberapa negara didunia diantaranya dengan melakukan pengembangan modifikasi alat tangkap trawl melalui perbaikan peningkatan selektivitas sehingga dapat mengurangi hasil tangkap sampingan yang dibuang kelaut. Peningkatan selektivitas alat tangkap trawl udang dapat dilakukan dengan cara : 1) modifikasi dari bentuk mata jaring (mesh shape) dari bentuk diamond menjadi square mesh; 2) memperbesar ukuran mata jaring; 3) memasang Bycatch Excluder Device (BED) atau Bycatch Reduction Device (BRD) dengan memanfaatkan tingkah laku ikan untuk meloloskan ikan yang bukan menjadi tujuan penangkapan (Broadhurst, 2000).