A-Shark movements

Habitat use, home range and site-fidelity 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.

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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.

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I use acoustic telemetry to assess the short and long-term movement patterns of sharks as well as habitat and space utilisation, home range.

Passive remote listening stations (VR2):

Some blackfin reef sharks were tagged with coded acoustic transmitters attached to the shark that emit signals about every 40 seconds. Ten data logging receivers (Vemco VR2 models) were deployed around Moorea Island and recorded the presence of every tagged shark that swam in their proximity.

Main results:

Blacktip reef sharks show strong site fidelity with mean 89% of detections for each individuals occuring at one receiver (41 – 100%). On average (N=34 individuals), sharks spent 13% of their time in a receiver’s detection range, with the highest fidelity being 75%. They usually use two sites moving from one to the other on a periodic daily basis.

Other results will come soon…

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