Macroscopic and Microscopic Characteristics of Ovarian Status of Female Veda Fish (Nandus nandus)

Abstract

Developmental changes in the macroscopic and microscopic characteristics of the ovarian status of female Veda, Nandus nandus were examined from the wild stock at Kawadighi haor over the 12 months period. Ovarian development status was assessed macroscopically and microscopically and histological analysis was used to establish the stages of oocyte development in a single ovary. Macroscopically, four development stages of oocytes were identified as immature, initial maturation, intermediate maturation and mature stages. The gonadosomatic index (GSI) gradually increased from January to July and reached a maximum value in September (11.22±0.68). The lowest GSI (%) value was observed in November (1.19±0.20). Vertical and horizontal ovipositor diameter displayed a positive relationship with ovary weight where R 2 2

= 0.557 and R = 0.734 respectively. The highest value of horizontal and vertical ovipositor diameter were 0.32 mm and 0.41 mm respectively in September. The highest hepatosomatic index (HSI) was observed in May (2.42±0.63) and lowest value was observed in October (1.07±0.23). The viscerasomatic index (VSI) did not follow any trend and fluctuated over the study period in which the highest value was found in January (5.45±2.93) as well as the lowest value was observed in October (1.86±0.12). The fish length and fish weight also showed strong positive relationship (R 2

0.925) indicating that the total length increased significantly with the increase of the total weight. The absolute fecundity was found to be 26536±5672 where the fish weight and fish length were 43.54±12.52 gm and 13.42±1.37 cm respectively. In the histological analysis of ovarian oocytes, more than two different development stages of oocytes co-existed in a single ovary indicated that N. nandus possesses a group asynchronous ovaries this means that the fish could spawn several times in a spawning season. The peak reproductive season of N. nandus may in August to September in wild condition based on the macroscopic and microscopic observation of ovaries. This study may contribute towards developing strategies for broodstock management in hatcheries as well as conservation and protection for sustainable aquaculture practice in haor based fisheries.