Contrasting trends in populations of rhopilema esculentum and aurelia aurita in Chinese waters

Rhopilema esculentum and Aurelia aurita are the most common scyphozoan species in Chinese waters. Here the population trends of R. esculentum and A. aurita are described and compared. The possible causes of their contrasting population trends are discussed by reviewing the status of existing information and introducing new data collected on blooms and reproduction of A. aurita in northeastern China. The population change of R. esculentum was described based on the annual harvest of R. esculentum in Chinese waters since 1955. It is generally accepted that a stock enhancement program has been successful in increasing the total catches of R. esculentum. However, the catches have declined since 1998, and this may be due to current stock enhancement levels exceeding the carrying capacity of the fishery ground or deterioration in the coastal marine environment. In contrast, blooms of A. aurita are causing increasing problems in the coastal waters of northern China with suitable settlement substrate provided by expansive coastal aquaculture implicated in these population increases. In addition to anthropogenic influences such as fishing, stock enhancement, and the proliferation of coastal infrastructure, the variation in reproductive and life history traits between R. esculentum and A. aurita may also explain the different recruitment potentials of the two species.