Observations of Reproductive Biology and the Gonadal Cycle of Endangered Nandus nandus (Hamilton, 1822)

Abstract

A study was conducted to determine the breeding season of endangered Nandus nandus by observing fecundity, somatic indexes, and gonadal cycle development year-round. Samples were collected from different fish landing centers of Sadar Upazila of Gazipur district. GSI values of N. nandus ranged from 4.26 ± 0.45 to 10.28 ± 0.39 while the maximum and the minimum GSI values were observed in July and in October, respectively. However, GaSI values showed an inverse relationship between them. The fecundity of this fish varied from 11176 ±593 to 18030 ± 1704 with the mean fecundity value of 13534.87 ± 87.53. Interestingly the highest fecundity was 18030 ± 1704 in July and the lowest fecundity was 11176 ± 593 in March, implying that the fecundity increased with the increment of time. Histological observation of ovary confirmed the presence of undeveloped oocyte (UO) to mature (M) stages of oocytes in fishes from March to November. The mature stages of oocytes including yolk vesicle’s (YV), yolk granule’s (YG), and in the case of the male predominance of spermatozoids were found high in proportion during June to July indicating the peak breeding season of N. nandus. Finally, these results suggest that N. nandus may breed from March with the peak in July and this information may help to provide a guideline for induced breeding and proper management of this fish in a controlled system as well as for conservation from being extinct.