Project Title : Conservation of horseshoe crabs in Hong Kong

Applicant : City University of Hong Kong (Drs. Paul Shin, S G Cheung and Richard Kong)

Total Approved Grant : $337,177.75

Duration : 1/10/2004 to 30/6/2006

Project Status/Remarks : Completed

Scope :
The project aims to enhance the population of horseshoe crabs in Hong Kong through artificial breeding and restocking of juveniles, and investigations of the extent of human exploitation, species differentiation as well as production of educational materials for promoting conservation of these endangered species.

Summary of Findings/Outcomes :
From a territory-wide survey of 17 shores, juvenile Tachypleus tridentatus were present on 11 shores on the west/northwest whereas Carcinoscorpius rotundicauda were found at 3 shores on the west/northwest and 1 shore on the northeast of Hong Kong. As compared to a similar study in 2002, a decline in juvenile T. tridentatus populations was apparent. Morphologically, T. tridentatus and C. rotundicauda were significantly different in various ratios of body parts. However, for phylogenetic comparison, the inter-specific variations of 18S and 28S rDNA sequence were very small. Both juvenile T. tridentatus groups with 1 and 3 immovable spines on the dorsal surface of the opisthosoma were also genetic closer to C. rotundicauda but morphologically closer to adult T. tridentatus. Other genetic sequences are thus needed to ascertain their identity. For human exploitation, the sale of horseshoe crabs was low compared to other commercial marine species. There was, however, a seasonal trend in demand. Education to discouraging the public to keep/consume horseshoe crabs will be necessary to protect the existing populations in local waters. It was also successful in artificially breeding of juvenile horseshoe crabs with optimal hatching temperature and salinity, but high mortality of the juveniles remained a difficulty to overcome.