Gonadal Maturity of Rainbow Trout (Oncorhynchus mykiss) Naturally Inhabited in Balkhila Stream of Uttarakhand, India

Abstract

In this study an attempt has been made for evaluating the gonadal maturity in the natural stock of rainbow trout inhabited in Balkhila stream of Alakhnanda river at Chamoli district of Uttarakhand, India. In collected stock, about 80% specimen showed full gonadal maturity, which reflects the conducive conditions for the gonadal maturity. The Gonadosomatic index (GSI) values of female rainbow trout ranged from 0.42 to 22.84 with a peak in January and reached its lowest level in March. In case of males, observed minimum value of GSI was calculated as 0.27 during the month of May, whereas the maximum value was 3.44 in the month of December and persisted in month of January and February also with the almost similar values. GSI values reflected the maturity of females during the month of January and February, while males became mature one month advance and remained mature during the December to early March. Hence, non- synchronization situation was observed in the gonadal maturity of both the sexes, which adversely affected the duration of breeding season and is a subject to a further study. In this study, the ovarian and testicular development of rainbow trout showed distinct stages. The oogonia and spermatogonia pass through a number of maturation stages finally leading to the formation of ripe ova and sperms.