Grey reef shark
OPEN DIVING LICENSE OBLIGATION
The expedition is dedicated to the project: “Nursery Monitoring Grey reef sharks“.
Since 2018, the CSS has activated this new project, dedicated to monitoring the presence of mature females and young newborns in a shoal located off the island of Nosy be in Madagascar, likely Nursery area of the Grey reef sharks (Carcharhinus amblyrhynchos).
Data collected about, the size of the population, characterization of individuals, stages of maturity, behavior. The Project is realized with the collaboration and logistic support of the Manta Diving, within the Technical-scientific Partnership signed between CSS and Manta Diving.
NEXT EXPEDITIONS IN PROGRESS:
2020 APRIL MADAGASCAR
Grey reef shark (Carcharhinus amblyrhynchos) is found in clear tropical waters, 10/50 m around coral reefs, in particular near drop-offs and coral reef passages. It is more common in ancient atolls and less common in high-profile islands with large human dwellings or in murky continental waters (Randall 1986, Wetherbee et al., 1997). In unexploited sites the Gray Reef Sharks are one of the most common tropical reef sharks that can be found in groups or individually. Potentially dangerous when harassed, they have been shown to show stereotypical threats (Johnson and Nelson 1973, Nelson 1981, Randall 1986).
Grey reef sharks, are included in the IUCN red list as near threatened, however, their biology is still relatively little known. Discordant data are available on their tendency to be site fidelity, studies carried out in Australia indicate limited reef fidelity and evidence of large-scale movements within northern Australian waters, while site fidelity and residency of grey reef sharks on the outer slope of coral reefs in Palau, Micronesia, over a period of two years and nine months were detected regularly throughout another study and sharks displayed strong inter-annual residency with greater attendance at monitored sites during summer than winter months. However, it is commonly believed that Grey reef sharks display strong levels of site fidelity that persist across years, at least for some components of the population. Site fidelity is a common phenomenon in many species, including whitetip (Triaenodon obesus), tawny nurse (Ginglymostoma cirratum), blacktip (Carcharhinus melanopterus), Caribbean (C. perezi) sharks. The degree of fidelity appears to vary according to life history stage, availability of resources and area of suitable habitat. Site fidelity is also common in adult reef sharks, although typically more sporadic when compared to juveniles, which might be partially explained by ontogenetic increases in the size of home ranges. Off Nosy be in Madagascar in the Mozambique channel, we have identified a new probable nursery that is being monitored by CSS since 2017, thanks to the logistical and underwater support of the Manta Diving. Around the pinnacle of a coral reef at about 15-30metres deep, grey reef sharks patrol daily, specimen sizes between 50cm and 200cm. The importance of identifying and reporting nursery areas for this species, is a priority to promote its proper conservation.