Age and growth of bullet tuna, Auxis rochei (Risso), from the Turkish Mediterranean coasts
The study aims to identify the age and growth parameters of bullet tuna (Auxis rochei) in Turkish waters. The fish were caught from the Turkish Mediterranean coasts between December 2008 and December 2009. A total of 186 dorsal fin spines obtained from the specimens were analyzed for ageing and growth studies. The fork length of the aged individuals ranged from 34 to 48 cm for males and from 35 to 46.5 cm for the females. Fish ages ranged 1 to 5 years old and the mean lengths by age were calculated for both sexes. Growth parameter estimates were calculated from 150 cut spine sections which provided readable growth annuli by sex. The growth parameters based on standard von bertalanffy growth function are the following: for males, L∞ (asymptotic length) is equal to 60.417 cm; k (growth coefficient) is equal to 0.159; t0 (age at zero length) is equal to − 4.311; for females, L∞ is equal to 49.238 cm; k is equal to 0.312; t0 is equal to −3.011; for both sexes, L∞ is equal to 57.388 cm; k is equal to 0.181and t0 is equal to −4.155, respectively. The length and weight relationship was calculated with W equal to 0.0542 L2.68.
Key words: Bullet tuna, Auxis rochei, age determination, growth, the Mediterranean sea.