Abstract
The study aims to identify the age and growth parameters of bullet tuna ( Auxis roche i) 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; t 0 (age at zero length) is equal to − 4.311; for females, L∞ is equal to 49.238 cm; k is equal to 0.312; t 0 is equal to −3.011; for both sexes, L∞ is equal to 57.388 cm; k is equal to 0.181and t 0 is equal to −4.155, respectively. The length and weight relationship was calculated with W equal to 0.0542 L 2.68 . Key words : Bullet tuna, Auxis rochei, age determination, growth, the Mediterranean sea.
Highlights
The genus Auxis distributes worldwide in tropical and subtropical waters
The growth parameters based on standard von bertalanffy growth function are the following: for males, L∞ is equal to 60.417 cm; k is equal to 0.159; t0 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
A total of 216 of bullet tuna were collected during the study period
Summary
The genus Auxis distributes worldwide in tropical and subtropical waters. Bullet tuna (Auxis rochei) is an epi and meso-pelagic fish that has a seasonal coastal distribution in temperate and tropical areas including the Mediterranean (Uchida, 1981; Collete, 1986; Valeiras and Abad, 2010). Bullet tuna is exploited mainly by surface gears and artisanal fisheries as trolling lines, handlines, small-scale longlines, and a wide variety of nets, especially traps, gill or drift nets, ring nets, beach seines, otter trawls, and purse seines. In some of these fisheries, Auxis species are taken incidentally as by-catch as in purse seine fisheries for yellowfin and skipjack tuna (Valeiras and Abad, 2010). The bullet tuna is one of the most abundant small tuna species in Turkish waters where has been
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