Of the three extant Asian species — tri-spine horseshoe crab (Tachypleus tridentatus), coastal horseshoe crab (T. gigas), and mangrove horseshoe crab (Carcinoscorpius rotundicauda) —, tri-spine horseshoe crab has been harvested commercially since the 1980s for the production of Tachypleus amebocyte lysate to safeguard vaccines, injectable drugs and other pharmaceutical devices from bacterial endotoxin contamination. 

Nowadays, the tri-spine horseshoe crab is listed as Endangered on the IUCN Red List of Threatened Species^TM, whereas the other two species are currently under reassessment. Asian horseshoe crabs are legally protected in Mainland China, India, Bangladesh, Vietnam, Singapore, and several regions in Japan, although the effectiveness of enforcement is largely unknown. 

The lack of baseline population data was identified in the tri-spine horseshoe crab Red List assessment as a major impediment to species conservation, a problem that also applies to the coastal and mangrove horseshoe crabs. These issues, and concerns regarding inconsistent sampling methods and data reporting in baseline population studies were also discussed at the Fourth International Workshop on the Science and Conservation of Horseshoe Crabs 2019 in Guangxi, China. Such deficiency hinders the feasibility of robust monitoring and assessment of Asian horseshoe crab population status for implementation of effective regional conservation actions. 

In 2021, HCSG initiates the “Asian Horseshoe Crab Observation Network” program to facilitate the long-term systematic monitoring of Asian horseshoe crab populations. In the first phase, the program is implemented in Mainland China and Hong Kong region in partnership with 12 local colleges, research institutes, marine protected area management units, and green groups. Funded by Zhilan Foundation from Shenzhen, China and other financial sources, 17 monitoring stations have been established along the Chinese shoreline, including provinces (regions) of Fujian, Guangdong, Guangxi, Hainan, and Hong Kong. 

While gathering baseline data on adult horseshoe crab populations is challenging due to their wide subtidal habitat range, collecting the long-term, reliable juvenile population information at representative nursery habitats can be considered as the first important step in the quantitative assessment of their population status. In this program, a locally-adapted standard for collecting and reporting juvenile population data is developed, together with on-site training and technical support. Public conservation education and citizen-scientist activities are also encouraged to maximize the involvement of local coastal communities and governmental agencies. 

The second phase of the program, to begin in 2022, will be implemented in Southeast Asian countries such as Malaysia, Singapore, and Indonesia. In the long run, important population information, including the distribution, size, and trend of the core populations across the range, would be obtained to help filling the baseline gap for Asian horseshoe crab conservation and status assessment.

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Contributors:

Kit Yue (Billy) Kwan, PhD., is a professor at the College of Marine Science and Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, Beibu Gulf University, Qinzhou, China. Co-Leader of the Asian Horseshoe Crab Working Group. 

Mark L. Botton, PhD., is a professor at the Department of Natural Sciences, Fordham University, New York, USA. Co-Chair of the IUCN SSC Horseshoe Crab Specialist Group (North America).

Paul K.S. Shin, PhD., is a retired associate professor at the Department of Biology and Chemistry, City University of Hong Kong, Hong Kong. Co-Chair of the IUCN SSC Horseshoe Crab Specialist Group (Asia).