Reproductive biology of a small amphidromous shrimp Atyoida serrata on Reunion Island,south-west Indian Ocean

Atyoida serrata is a small amphidromous shrimp distributed in the south-west Indian Ocean. This species is threatened by human activities such as fisheries and river discharge withdrawals. Knowledge of its reproductive biology is essential to develop management plans and reduce the impacts of these threats. This study presents the results of a one-year survey in three stations along the Langevin River, Reunion Island. Densities of shrimps dominated by juveniles decreased with an increasing altitude. However, the largest individuals were more numerous upstream. Despite variable size structures among stations, all the largest individuals were females. Females larger than 32 mm Total Length had a probability of 50% or more of being ovigerous. Fecundities were ranged from 271 eggs for a 28 mm TL female to 4,365 eggs for a 47 mm TL female. Reproductive activity was observed throughout the year with a considerable increase from September to April. This increase was positively correlated to day-lengths and to a lesser extent to elevated water temperatures and river discharges. This study suggests a fishing restriction in the upstream areas and during the reproductive season. Attention should be paid to management of water withdrawal during low water levels to reduce impacts on the larva drift.