Movement and group structure in wild blackfin reef sharks, Carcharhinus melanopterus, at Moorea,
Johann Mourier and Serge Planes
Centre de Recherche Insulaire et Observatoire de l’Environnement (CRIOBE), BP 1013, 98729 Papetoai, Moorea,
The blackfin reef shark (Carcharhinus melanopterus) is the most abundant shark species of Polynesian reef communities. Despite its abundance, many aspects of its basic natural history remain poorly or incompletely documented. The blackfin reef shark, neither a solitary nor a schooling fish, is often seen in small aggregations, especially when feeding. Such group living is commonly observed in shark populations, but relatively little is known about the overall organisation, structure, and complexity of these groups. Using a combination of approaches including tagging, photo-identification and genetics, this study aimed to document whether reef shark population organisation is structured or random. Twenty blackfin reef sharks were tagged with Vemco Rcode acoustic transmitters (model V16) and six Vemco VR2 acoustic receivers were deployed. Preliminary results show that sharks demonstrate a high degree of site fidelity with small home ranges. These results suggest that stable group living may be present in this species in the wild. On different sites around the island of Moorea, sharks were caught, photo-identified and DNA sampled for microsatellite analysis. Subsequent underwater surveys using distinctive markings to identify individuals, combined with our genetic results enabled group composition and relatedness to be analysed. Our research will determine whether shark groups are composed of close relatives or are randomly structured.