Effects of rubble zones from oyster cultivation on habitat utilization and foraging behaviour of the endangered tri-spine horseshoe crab: An implication for intertidal oyster cultivation practices. (1st October 2020)

• Record Type: Journal Article
• Authors: Kwan, Kit Yue; Wong, Wang Tang; Lam, Po Yan; Chan, Hoi Kin; Lo, Hoi Shing; Cheung, Siu Gin
• Is Part Of: Journal of environmental management. Volume 271(2020)
• Publication Date: 2020-10-01
• Subjects: Tri-spine horseshoe crab -- Nursery ground -- Oyster aquaculture -- Utilization distribution -- Foraging behaviour; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2020.110925
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Estuarine structured habitats, including benthic cultivation structure, are widely cited as substantial nursery and feeding grounds for fish and macroinvertebrates. Activities such as locomotion and foraging behaviour of sediment-dwelling species, however, may be hindered in the presence of the obstacles. In this study, collected field evidence demonstrated that habitat utilization of the juvenile tri-spine horseshoe crab Tachypleus tridentatus, an iconic and endangered macroinvertebrate, was adversely affected by high-density intertidal oyster rubble zones. Despite the fact that the utilization area of individual juvenile horseshoe crabs was independent of the presence of these obstacles, the abundance and number of positional fixes of tagged juveniles in these areas were lower. The effects of these obstacles and their associated topographic changes on the movement of the juvenile horseshoe crabs was investigated in a simulated laboratory experiment. Both the simulated oyster cultches and hummocks formed between the cultches reduced the total distance and displacement of the feeding trail, and less juveniles preferred to forage on elevated, dry hummocks (dry at low tide) formed between the cultches. Our findings suggested that oyster cultches and rubbles reduced the habitat quality for juvenile horseshoe crabs. On-bottom oyster cultivation activities seeking to conserve horseshoe cabs by avoiding nursery habitats should instead consider off-bottom or offshore cultivation methods. Highlights: Horseshoe crabs are ecologically significant in coastal and estuarine ecosystems. Intertidal oyster rubbles affected foraging behaviour of juvenile horseshoe crabs. Laboratory studies confirmed the localized effects of physical structure additions. On-bottom oyster culture not recommended on nursery habitats of horseshoe crabs.