Seafood harvesting practices in critical nursery habitat of Asian horseshoe crabs in northern Beibu Gulf, China: Suggestions for conservation management

Mangrove forests are among the most productive ecosystems. Horseshoe crabs, an ecologically important marine taxon, are particularly reliant on this ecosystem. However, their populations are increasingly threatened across the geographic range, especially the three Asian horseshoe crab species in Indo-Pacific Asia. Unlike explicit habitat loss, implicit threats caused by artisanal fishing remain largely unrecognized for these Asian species. Seafood harvesting in intertidal zone (SHIIZ) is among the dominant artisanal fishing activities in China. In this study, we quantified the intensity and spatiotemporal patterns of SHIIZ at a critical nursery habitat for horseshoe crabs in a multi-use protected area of the northern Beibu Gulf, China. Adopting drone-based line transects, we surveyed the entire unvegetated tidal flats to estimate harvesting intensity from October 2022 to September 2023 at monthly intervals across the three study sites. Our results demonstrated significant differences in collection intensity among the three sites, with higher intensity from October 2022 to March 2023. Overall, fishers exerted greater intensity than tourists. Across the sites, fishers primarily utilized the middle/lower portions of tidal flats, while tourists aggregated near the mangrove fringes. Despite fishers being the primary contributors, management should focus on the tourists, as their activities significantly overlapped with the core distribution areas of juvenile horseshoe crabs along the mangrove fringes during active season. We recommend quota control, pre-entry education, and real-time guidance to mitigate potential impact of tourists’ seafood harvesting. Strengthening collaboration between management authorities of the study area and local communities would enhance effective implementation of these proposed measures.