Habitat use, home range and island or region scale movements of sharks
Knowledge of movement patterns (i.e. use of space and activity patterns) is essential in understanding the behaviour of a species as well as defining essential habitat for that animal. An animal’s movement patterns will affect its metabolism, reproductive fitness, and survival. Currently, little is known about either biological process for most shark species, due in large part to the difficulties in studying these animals in the wild and in captivity. Blackfin reef sharks as with many other shallow water or coastal reef sharks use nursery areas during their early years of life because of low predation rates, high abundances of prey, and suitable habitat. When growing, reef sharks increase their home range and their habitat variability to the lagoon and the outer slope of the reef.
In the context of increasing tourism, coastal habitat degradation, over-exploitation in relatively small Island of French Polynesia, understanding the movement patterns of sharks is essential for effective management, and for designing the spatial extent of marine reserves to optimize conservation of these ecologically important and mobile predators.
I will use a combination of telemetry tracking, satellite tracking and genetic approaches to assess the short and long-term movement patterns of sharks as well as habitat and space utilisation, home range, and migrations between islands.
Active real time acoustic tracking:
Some blackfin reef sharks will be tagged with active, continuous acoustic transmitters attached to the shark. These sharks will be tracked using a hydrophone and receiver from a small flat-bottomed boat. Every 5 minute of tracking, the GPS location of the boat and an estimated distance to the shark will be recorded. Every 30 minutes, environmental data (e.g. water temperature, current, surface conditions, tidal stage) will be record.
Some juvenile sicklefin lemon sharks as well as blackfin reef sharks will be tracked in their nursery area in order to better understand their use of nurseries.
In order to understand:
• Short term movement
• Real time movements
• Home range, habitat use
Passive remote listening stations (VR2):
Some blackfin reef sharks will be tagged with coded acoustic transmitters attached to the shark that will emit signal about every 40 seconds. Six data logging receivers (Vemco VR2 models) will be deployed in different sites of Moorea Island and will record presence of every tagged shark that swim in their proximity.
Listening stations will give me information such as:
• Presence/absence data
• Long term movement
• Frequentation, site fidelity and habitat use
Inter-Island migrations:
French Polynesia is constituted by patches of small islands separated by oceanographic or geological barriers (rapid coastal bottom drop to down to 2000 – 3000 m depth). Most of reef sharks are observed living in lagoon and outer slope habitats of Island and Atolls. But are these “coastal” sharks migrate much farther than we think to other Islands, even across the open ocean?
I will use a combination of satellite tracking (pop-up archival satellite tags) and genetic approaches to assess possible inter-island migrations.
