Fishery, biology and dynamics of dogtooth tuna, Gymnosarda unicolor (Rüppell, 1838) exploited from Indian seas

Abstract

The fishery and dynamics of dogtooth tuna Gymnosarda unicolor (Rüppell, 1838) exploited along the Indian coast was studied. The species was landed mainly in Kerala, Andaman & Nicobar and Lakshadweep, exploited mainly by hooks and line and the catch showed an increasing trend. The average annual landing by coastal fishery was 130 t (2006-2010) and by Letter of Permit (LOP) vessels was 1,311 t. Size in the catch ranged from 32.5 to 162.0 cm in fork length (FL). The length weight relationship was W=0.0105 L 3.065. The von Bertalanffy growth parameters (VBGF) estimated using ELEFAN of FiSAT software were L∠= 163.6 cm, K=0.43 yr-1, t0= -0.12. Estimated total mortality, natural mortality and fishing mortality were 1.06, 0.572 and 0.49 respectively. The estimated tmax was 12 years and it reaches 56.6 cm, 94.0 cm, 118.3 cm, 134.1 cm, 158.3 cm, 162.6 cm in 1, 2, 3, 4, 8 and 12 years respectively. The species mature and spawn round the year with peak during August-January. The estimated biological indictors of the species are Lm= 69.0 cm; Lm/Lâˆ=0.4217; Lopt = 75.8 cm, Lopt/L∠=0.463 and Wâˆ= 64.0 kg. Fecundity estimated for the species was 3, 15, 244 per kg body weight. Young recruits enter the fishing grounds during most part of the year with peak during February-May. Along the Lakshadweep coast, G. unicolor was mainly exploited during September - March. The fishery data suggest that they are available in large numbers along the Andaman and Nicobar area.