Age and growth of bullet tuna Auxis rochei (Risso, 1810) in Turkish waters


Deniz T. , Oray I. K.

Presentation, pp.1-11, 2000

  • Publication Type: Other Publication / Presentation
  • Publication Date: 2000
  • Page Numbers: pp.1-11

Abstract

In this investigation, the length-weight relationships of Auxis rochei (Risso,

1810) commercially exploited in the Aegean and Mediterranean Seas from January

1994 to May 1996 were studied. The frequency distributions of 936 individuals were

analysed according to years and sexes. The relationships between the parameters were

determined by means of logarithmic regressions. The otolith readings and sections

from the first fin ray of the first dorsal fin were used for age determination. The

individuals ranged from 0. to V. age groups.Due to inadequate sample numbers (5),

the specimens of the age groups 0. were not included.

50.2% (311 individuals) of the 630 examined specimens (I. to V. age groups) were

females and 49.8% (309 individuals) were males. As the gonad conditions of the these

individuals could not be observed, the sexes of the 10 individuals mainly of the age group I

were not determined.

The average fork lengths of the combined females and males in accordance with the age

groups were 30.7 cm in the age group I; 34.43 cm in the age group II; 38.7 cm in the age

group III; 41.1 cm in the age group IV and 42.39 cm in the age group V. The L value was

47.76 cm for combined females and males; L value was 42.26 cm for females; the L value for

the males was 45.08 cm. The length-weight relationship was determined in accordance

with Le Cren’s (1951) allometric growth equation, namely:W=0.0076 L3.24291 for

combined females and males. The growth of Auxis rochei was found to be allometric.

The spawning period of this species in the Aegean Sea and in the Mediterranean Sea

was determined to be from March to September.