SEBARAN UKURAN PANJANG DAN NISBAH KELAMIN IKAN MADIDIHANG (Thunnus albacares) DI SAMUDERA HINDIA BAGIAN TIMUR

Abstract

Ikan madidihang atau tuna sirip kuning (Thunnus albacares) merupakan salah satu komoditas penting bagi industri perikanan di Indonesia dengan hasil tangkapan tertinggi dibandingkan jenis tuna lainnya. Sebagai dasar pengelolaan sumberdaya ikan yang berkelanjutan, diperlukan data dan informasi tentang komposisi ukuran layak tangkap yaitu membandingkan proporsi rata-rata ikan tertangkap (Lc) dan matang gonad (Lm), serta nisbah kelamin sebagai indikator pendugaan kemampuan memijah. Pengumpulan data dilakukanmelalui program observasi diatas kapal rawai tuna yang berbasis di Benoa, Pelabuhanratu dan Bungus dari bulan Agustus 2005 hingga November 2013. Penghitungan nisbah kelamin menggunakan uji Chi-Square (X2) dengan tingkat kepercayaan 95%. Hasil penelitian menunjukkan bahwa distribusi ukuran panjang cagak ikan madidihang berkisar antara 30-179 cm, modus ukuran 106-110 cm dan rata-rata 101,65 cm. Sebanyak 81,03% madidihang yang tertangkap berukuran lebih besar daripada Lm yang berarti telah layak tangkap. Nisbah kelamin betina:jantan adalah 1:1,45 mengindikasikan dominansi ikan jantan. Hubungan antara nisbah kelamin dengan panjang ikan menunjukkan signifikansi dimana ikan betina semakin berkurang pada ukuran 120-180 cm, serta tidak ditemukan lagi pada ukuran lebih dari 170 cm. Korelasi nisbah kelamin dan panjang cagak dapat dideskripsikan dengan persamaan regresi sebagai berikut: 1,8013 - 0,0099 FL dengan nilai R2=0,8058.

Yellowfin tuna or YFT (Thunnus albacares) is one of the important commodity for the fishing industry in Indonesia because it has the highest catches compared with other tunas. In order to fisheries resources management, it was necessary to monitor the size composition compared between proportion average size captured (Lc) and maturity size (Lm) to meets the size eligibility, as well as the sex ratio as an indicator to estimate the ability of spawn. Data collected by scientific observers program which was following tuna longline operation mainly based in Benoa, Palabuhanratu and Bungus Fishing Port, from August 2005 to November 2013. Chi-Square analysis with 95%confidence level also implemented to determine sex ratio between female and male. The result indicated that YFT were caught has size ranged between 30-179 cm, size mode ranged between 106-110 cm and the mean was 101,65 cm.Mostly YFT (81,03%) was greater than its maturity size (Lm) and that’s mean have been worthy to be captured. Sex ratio of (F:M) 1:1,45 was observed which indicates male was dominant. Correlation between sex ratio and length proved to be significant where the female was diminishing in size between 120-180 cm, even female was no longer found in size more than 170 cm. Correlation between sex ratio and length can described as a regression equation=1,8013 - 0,0099 FL; R2=0,8058.