Effects of Commercial Clamming on the Survival of Avicennia marina Seedlings in the Beibu Gulf, China

Abstract

Debate has continued between clammers and conservationists due to lack of scientific evidence establishing whether or not clamming is detrimental to the survival of mangrove seedlings. We examined the impacts of collecting mangrove clams (Paphia undulate) using a clam rake (CR) or basket rake (BR) tool on the survival of Avicennia marina seedlings in the Beibu Gulf, China. The quantity of seedlings which survived the clamming was monitored over a 24-month period under CR clamming, BR clamming and no clamming (CK) treatments. Results showed four categories of seedling disturbance after clamming were observed regardless of clamming method. These impact categories are intact, uprooted, stem snap and basal stem snap. Significant differences were found in the proportion of seedlings of uprooted, intact and basal stem snap between CR and BR (P < 0.05). We found none of intact, stem snap, basal stem snap under canopy survived 24 months after clamming. Additionally, uprooted seedlings were detected in the bare tidal flats, which survived and grew during experiment. Our results did not suggest that commercial clamming should be totally restricted in Beibu Gulf, as seedling disturbance in the present study did not appear to be directly related to clamming method. Additionally, we found that seedlings uprooted during clamming could provide dispersal and establishment opportunities for seedlings. Further investigations are required to fully isolate the implications of commercial clamming upon mangrove forest before any management decisions can be confidently made about these practices.