PENGARUH PERLAKUAN SUHU MEDIA BERBEDA TERHADAP VIABILITAS DAN PENETASAN TELUR IKAN TUNA SIRIP KUNING Thunnus albacares (Bonnaterre, 1788)

Abstract

Sejak tahun 2015 penelitian pembesaran larva ikan tuna sirip kuning (Thunnus albacares) hasil pemijahan di keramba jaring apung (KJA) berhasil memproduksi juvenil 500-1.000 ekor benih per percobaan. Permasalahan utama adalah daya tetas telur yang berfluktuasi karena suhu air media inkubasi tidak stabil. Penelitian bertujuan untuk menentukan suhu air yang optimum untuk mendapatkan daya tetas telur yang tinggi. Penelitian ini menggunakan sembilan bak fiberglass transparan berbentuk kerucut dengan volume 200 L diisi dengan 50.000 butir telur/bak pada stadia morula. Penelitian ini menggunakan rancangan acak lengkap dengan perlakuan suhu media awal ditambah kisaran yang berbeda yaitu (A) 28,7 ± 0,5°C; (B) 28,7 ± 1,0°C; dan (C) 28,7 ± 2,0°C; masing masing perlakuan dengan tiga kali ulangan. Hasil penelitian menunjukkan bahwa daya tetas telur tertinggi (42.500 ekor atau 85,3 ± 9,2%) pada perlakuan A dan berbeda nyata (P<0,05) dengan perlakuan B (22.500 ekor atau 44,6 ± 16,3%) dan C (12.000 ekor atau 24,0 ± 2,6%). Ukuran larva yang baru menetas pada perlakuan A, panjang badannya lebih panjang dan berbeda nyata (P<0,05) dibandingkan dengan perlakuan C. Peningkatan suhu menyebabkan peningkatan pemanfaatan kuning telur. Laju pemanfaatan kuning telur pada perlakuan (C) 28,7 ± 2,0°C mencapai 0,02 mm3 jam-1 dua kali lebih tinggi dibandingkan pada perlakuan (A) suhu 28,7 ± 0,5°C yang hanya 0,01 mm3 jam-1. Semakin tinggi peningkatan suhu inkubasi dari suhu awal, mortalitas embrio semakin tinggi (P<0,05) sehingga daya tetas telur ikan tuna berbeda nyata antar perlakuan. Direkomendasikan bahwa peningkatan optimum suhu untuk menstimulasi daya tetas telur ikan tuna sirip kuning yang lebih tinggi adalah 0,5°C dari suhu sekitar.

Since 2015, researchers from the Institute for Mariculture Research and Fisheries Extension, Gondol have successfully carried out larval rearing of yellowfin tuna (Thunnus albacares) produced from broodstocks spawning in floating net cages. The number of produced yellowfin tuna juveniles ranged between 500-1,000 juveniles per batch. One of the main problems in yellowfin tuna larval rearing is related to the fluctuation of eggs hatching rate due to unstable water incubation temperatures. The aim of the research was to determine the optimum temperature to obtain a maximum egg hatching rate. In this research, nine transparent cone-shaped fiberglass containers with a volume of 200 L were used and stocked with 50,000 eggs morula stage/tank. The experiment was arranged in a completely randomized design with the treatments described in the following. The ambient hatchery water temperature was 28.7°C and was increased at specific increment temperature settings as the treatments as follows: (A) 28.7 ± 0.5°C; (B) 28.7 ± 1.0°C; and (C) 28.7 ± 2.0°C. Each temperature treatment had three replicates. The results showed that the highest hatching rate of eggs (42,500 larvae or 85.3 ± 9.2%) was observed in treatment A. The result from treatment A was significantly different (P<0.05) than that of treatment B (22,500 larvae or 44.6 ± 16.3% and C (12,000 larvae or 24.0 ± 2.6%). The hatched larvae in treatments A has longer body length and was significantly different (P<0.05) compared to treatment C. The increase of temperature in each treatment has led to a rise in the yolk utilization rate. The yolk utilization rate in treatment (C) of 28.7 ± 2.0°C was 0.02 mm3 h-1, two times higher compared to treatment (A) 28.7 ± 0,5°C, which was only 0.01 mm3 h-1. The higher the incubation temperature, the higher the embryo mortality (P<0.05). Therefore, the hatching rate of tuna eggs was significantly different among the treatments. This research recommends that the optimum stimulating temperature increase to improve the hatching rate of yellowfin tuna eggs is 0.5°C from the ambient temperature.