Can Salinity Changes Affect Reproductive Success in the Brown Shrimp Crangon Crangon ?

Abstract

Abstract In coastal environments, salinity variations may affect phases in crustacean reproductive cycle. Brown shrimp Crangon crangon Linnaeus, 1758 (Decapoda) are known to undertake breeding migrations between the sea and coastal waters (lagoons, estuaries). After a major flooding, the salinity of the Vaccarès coastal lagoon (Rhône River delta, France) dropped from 15‰ to 5‰ in a few days and remained low during following years. The aim of this study was to assess the impact on this environmental change on the reproduction of brown shrimp. We first tested whether females C. crangon had the ability to become ovigerous at a salinity as low as 5‰. Furthermore, the question whether salinity had an impact on fecundity was addressed. Experiments in aquaria were carried out for 180 days in the laboratory, with three replicates at three salinities (5, 15, and 25‰ respectively), keeping local photoperiod and temperature. Mortality was significantly higher in tanks at 5‰ than in those at higher salinities. Females reared at 25‰ salinity started to become ovigerous after 32 days; at 15‰ ovigerous females were only recorded after 80 days. No female became ovigerous at 5‰. A brackish salinity (15‰) would delay ovarian development in C. crangon, whereas a low salinity (5‰) seemed to inhibit maturation. Fecundity was higher in females reared at 25‰ than in those reared at 15‰. Results are explained and discussed taking into account eventual trade-off between reproduction and maintenance activities. Experimental data suggest that a too-low salinity in brackish lagoons may affect reproductive success of migratory natant decapods, such as C. crangon.