Reproductive Biology of Yellowfin Tuna, Thunnus albacares (Bonnaterre, 1788) off Visakhapatnam, North Andhra Pradesh, India

Abstract

Tunas are epipelagic, highly migratory species that are widely distributed in the tropical and subtropical waters of the world. The present paper deals with some aspects of reproductive biology such as maturity stages, gonado - somatic index, spawning period, size at first maturity and fecundity of yellowfin tuna, Thunnus albacares from the area off north Andhra Pradesh. Thunnus albacares in this region showed two peak spawning seasons viz., during April-May and September-October. The size at first maturity of Thunnus albacares was estimated as 90 cm fork length for male and 90.1 cm fork length for females. The relations between the fecundity (F), fork length (L), body weight (W) and ovary weight (V) were found as F= 0.0007L4.56676 (r = 0.74), F= 10.615W1.6304 (r = 0.77) and F= 9.3054V1.0073 (r = 0.79).