Correlation analysis of migration in Eriocheir sinensis of the Yangtze River estuary based on salinity preference

Reproduction and development are the most important stages in the life of aquatic animals, which are also the most sensitive stages to environmental stress. As a migratory crab, parent Eriocheir sinensis need to migrate to estuary (brackish water) for reproduction, and megalopas need to migrate to freshwater for development. Yangtze River estuary is located at the junction of the Yangtze River and the East China Sea, and the salinity of different regions varies greatly (salinity 0-30‰). Therefore, salinity is one of the key environmental factors affecting E. sinensis. In this study, the salinity preference of parent and megalopas E. sinensis was observed and analyzed by the six-chambered and seven-chambered devices of laboratory experiments. Two groups of alternative salinity were set for parent crabs (7, 14, 21, 28, and 35 ‰) and megalopas (0, 5, 10, 15, 20, 25, and 30‰). The results indicated that males showed no obvious preference for salinity, while females had obvious preference for different salinity and stronger dependence and tolerance to saltwater. Megalopas showed a significant preference for low salinity which was beneficial to migrating to freshwater quickly. It was speculated that the behavior of megalopas tending to freshwater was an inherited behavior in the evolutionary process rather than influenced by environment. The salinity preference of E. sinensis might change the position of spawning grounds and migratory routes, and then the annual fluctuation of salinity in Yangtze River estuary will affect the change of E. sinensis resources.