Effects of prior acclimation on the survival, feed intake and salinity preference of a freshwater-adapted euryhaline crab

In estuarine systems, salinity changes by freshwater inflows and tides affect the survival and behaviour of euryhaline species. Juvenile Chinese mitten crabs, Eriocheir sinensis, are considered to live in fresh water during their complex life history, whilst some are found in coastal wetlands. To understand how juveniles disperse in estuarine residence, we investigated their survival, feed intake and salinity preference after acclimating in three different water situations (i.e., fresh water, salt water and alternation between fresh water and salt water). We supposed that behavioural alternation and salinity preference would play an essential role in their acclimation. Results showed no significant difference in survival and feed intake amongst the three groups of juveniles (P >0.05) in acclimation trials. However, the feed intake of crabs in each group was declining after changing water every three days. In the salinity preference experiment, crabs from fresh water preferred 0%o and 12%o, whereas those from salinity and alternation treatments showed no preference. The salinity preference seemed to be modified by prior acclimation as well, and juvenile crabs could therefore survive and disperse in the different salinities. Our study helps to explain the complex distribution of juveniles in estuaries and provides arguments for the feasibility of Chinese mitten crabs being reared in low salinity waters.