Spatial variation of the broodstock availability of Acanthopagrus berda (Forsskal 1775) with emphasis on seasonality, lunar periodicity, and sex ratio for facilitating efficient breeding program

Abstract

Successful breeding program for hermaphrodites needs planned broodstock collection. The presented work aims to study the dynamics of broodstock availability of Acanthopagrus berda along selected stretches of Indian coast to facilitate scientific broodstock management. Broodstock availability was recorded for three consecutive years from two geographic locations, Karwar [offshore (beach area) using shore seine and inshore (estuarine area) using hook and lines, cast net and gillnet] and Calicut (inshore using hook and lines, cast net and gillnet). In both regions, most of the stocks were collected between the post-monsoon and pre-monsoon seasons (August to March). At Calicut, a considerable quantity of broodstock was available during all lunar phases except the new moon phase, while at Karwar, it was available except for the first and third quarter and full moon with assured availability during the waxing and waning phases. At Karwar, in the shore seine, the broodstock was available only from August to November, but in cast net, the broodstock was available from August to February. The brooders collected from the Calicut coast were significantly (Welch's statistics p < 0.05, Hedge's g = 0.79) larger (25.476 ± 0.32 cm) than those obtained from the Karwar (21.64 ± 0.17 cm). The highest mean length was observed in the case of fish collected by hook and line, cast net and gill net at Calicut (25.47 ± 0.31), followed by cast net (21.79 ± 0.52) and shore seine (21.60 ± 0.17) at Karwar. The estimated length of sex reversal (L50) was 25.50 cm total length (TL) with a considerable overlap in sex category in the size range of 20 − 30 cm. Welch ANOVA (One-Way) for difference in mean length affirmed no significant difference, and hence the probability of getting a higher number of a particular sex during a given lunar phase could not be assumed.