Size structure and growth parameters of the frigate tuna (Auxis thazard) landed in the port of Antsiranana (2012 – 2019)

Frigate mackerel (Auxis thazard) is a pelagic fish and belongs to a member of the family Scombridae. It is found in almost all tropical and subtropical seas. In the period 2012-2019, 18 997 Auxis thazard were sampled, from the bycatch of European seiners who landed at the port of Antsiranana. The individuals are identified and measured according to the length at the fork (LF). The LFDA 5 program was applied to assess biological characteristics. The size frequency is dominated by the size between 40 cm and 42 cm. The estimated parameters of growth using the equation of Von Bertalanffy are: L∞ = 48.41 cm and the K = 0.53 year-1, t0 = -0.071. The results also showed that total mortality Z and natural mortality M were 0.95 years-1 and 0.71 years-1, respectively, while fishing mortality F was 0.24 years-1.