Structure and growth pattern of yellowfin tuna Thunnus albacores (Bonnatere, 1788) in the waters of Simeulue Islands, Aceh

Abstract

Yellowfin tuna (Thunnus albacores) is a large pelagic fish originating from the Scombridae family. This fish can be found almost in all tropical and subtropical waters even often found in Indonesian waters, especially the waters of Semeulue islands. Data pertaining to the growth pattern of the fish are meaningful as a reference for tuna fish resource management in Semeulue waters. This research aimed to investigate the current condition of tuna growth through understanding the size and growth pattern of yellowfin tuna in Simeulue waters. The study was conducted for 4 months from August to November 2016 in Simeulue waters in fisheries managemen area 572. Fork length (FL) of yellowfin tuna was randomly collected on a weekly basis using a roll meter (5 m). The fish length frequency for the determinationof class interval was obtained using frequency distribution formula, while a FiSAT II program was employed to observe biological properties of the fish. A total of 85 yellowfin tuna was successfully assessedusing a fishing pole in the waters of Semeulue Islands (Lasia Island and Babi Island). This number was relatively small because of weather factors; the fishersdecided not to catch the fish in the sea. The results showed that fork length of Yellowfin tuna was 45.5-111.5 cm. Furthermore, length frequency of Yellowfin tuna was assessed using von Bertanlanffy growth functions. Maximum length (L∞) of the fish reached 117.08 cm, while K value was 0.93 per year, theoretical age of 0.10 years and growth prospecting index (O) of 4.10. The analysis using length-converted catch curve showed total mortality (Z) of 2.11, natural mortality (M) of 1.22, with an average temperature of 31 °C, capture mortality (F) of 0.89, exploitation rate (E) of 0.42 per year.