Asian Horseshoe Crab Bycatch in Intertidal Zones of the Northern Beibu Gulf: Suggestions for Conservation Management

Wang, Chun Chieh; Chen, Ruifang; Yang, Xin; Wen, Yulong; Kuang, Yang; Zhang, Ce; Zhu, Junhua; Kwan, Kit Yue

doi:10.1007/s11802-022-5214-9

Cited by 6 publications

(1 citation statement)

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“…However, horseshoe crabs are heavily harvested for their blood for the manufacture of Tachypleus and Limulus amebocyte lysates, the worldwide standardized tests for bacterial endotoxin detection in pharmaceutical products ( Gauvry, 2015 ; Tinker-Kulberg et al, 2020 ). In addition to resource exploitation, habitat loss and degradation from coastal development ( Tsuchiya, 2009 ; Nelson et al, 2015 ; Wang et al, 2020 ), as well as bycatch by artisanal fishing and discarded fishing gear, are also widely observed to cause considerable threats to horseshoe crab populations ( Zauki et al, 2019 ; Wang et al, 2022 ). The Atlantic horseshoe crab Limulus polyphemus and tri-spine horseshoe crab Tachypleus tridentatus are listed as “Vulnerable” ( Smith et al, 2016 ) and “Endangered” ( Laurie et al, 2019 ), respectively, in the IUCN Red List of Threatened Species, while the status of other two Asian species, the coastal horseshoe crab T. gigas and mangrove horseshoe crab Carcinoscorpius rotundicauda are under reassessment owing to the recent reports describing substantial population declines ( John et al, 2018 ; Wang et al, 2020 ).…”

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Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast

Kwan

Yang

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et al. 2022

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Background An enhanced understanding of larval ecology is fundamental to improve the management of locally depleted horseshoe crab populations in Asia. Recent studies in the northern Beibu Gulf, China demonstrated that nesting sites of Asian horseshoe crabs are typically close to their nursery beaches with high-density juveniles distributed around mangrove, seagrass and other structured habitats. Methods A laboratory Y-maze chamber was used to test whether the dispersal of early-stage juvenile tri-spine horseshoe crab Tachypleus tridentatus is facilitated by chemical cues to approach suitable nursery habitats. The juvenile orientation to either side of the chamber containing controlled seawater or another with various vegetation cues, as well as their movement time, the largest distance and displacement were recorded. Results The juveniles preferred to orient toward seagrass Halophila beccarii cues when the concentration reached 0.5 g l−1, but ceased at 2 g l−1. The results can be interpreted as a shelter-seeking process to get closer to the preferred settlement habitats. However, the juveniles exhibited avoidance behaviors in the presence of mangrove Avicennia marina and invasive saltmarsh cordgrass Spartina alterniflora at 2 g l−1. The juveniles also spent less time moving in the presence of the A. marina cue, as well as reduced displacement in water containing the S. alterniflora cue at 1 and 2 g l−1. These results may explain the absence of juvenile T. tridentatus within densely vegetated areas, which have generally higher organic matter and hydrogen sulfide. Conclusion Early-stage juvenile T. tridentatus are capable of detecting and responding to habitat chemical cues, which can help guide them to high-quality settlement habitats. Preserving and restoring seagrass beds in the intertidal areas should be prioritized when formulating habitat conservation and management initiatives for the declining horseshoe crab populations.

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