Published Paper Details:

The focus of the study was to observe reproductive biology of three neritic tunas viz., Thunnus tonggol, Euthynnus affinis and Auxis thazard belonging to the family Scombridae during the period 2009-2012. A total of 512 samples of Thunnus tonggol, 448 Nos. of Euthynnus affinis and 586 Nos. of Auxis thazard were analysed for the study. The development of ova from immature to maturity levelrevealed that, in IIIrd stage, the maturing ova measured between 0.039-0.068mm in Thunnus tonggol, 0.008-0.028mm in Euthynnus affinis and 0.008-0.024mm in Auxis thazard. Two distinct spawning seasons were observed in all the three species and major spawning season for these species was observed during August-December. Minor spawning season was during March-May in T. tonggol, March to May in E. affinis and January-April in A. thazard. The size at first maturity in T. tonggol was recorded at 48.0cm, E. affinis at 42.0cm and A. thazard at 37.5cm. Male to female sex ratio was 1:1.3 (T. tonggol), 1:1.7 (E. affinis) and 1:1.1 (A. thazard). The gonado-somatic index values were in the range of 0.042-5.826 for all the three species. Fecundity of T. tonggol was between 1,43,230-22,30,000 ova, E. affinis range was 2,15,759-15,63,721 and in A. thazard, 89,400-15,99,528.