Population dynamics of the rock shell Reishia clavigera associated with different degrees of organotin contamination in Hong Kong.

Application of organotins in antifouling systems on ship hulls has been globally prohibited by the International Maritime Organization since September 2008. It is, therefore, anticipated that there is a recovery of imposex-affected gastropod populations worldwide. We studied the population dynamics of the rock shell Reishia clavigera in six locations around Hong Kong's coastal waters, covering different degrees of organotin contamination for 25months (2011-2013). Abundance and density of R. clavigera were higher in clean sites, while they tended to grow faster in polluted sites. Over time, we observed recruitments in clean sites while recruitments in polluted sites were limited. The results suggested that the lack of apparent recovery of the local R. clavigera populations was probably due to the prevalence of organotin contamination, especially triphenyltin, in this region. This study, therefore, calls for mitigation and long-term monitoring of organotin contamination in marine environments of Hong Kong and South China.