Impact of « shark feeding » activities on shark behaviour and ecology
The feeding of wildlife has become a popular means by which tourists and tourism operators can facilitate close observation and interaction with wildlife in the wild. Compared to marine pollution, coastal habitat degradation, over-exploitation and intensive fishery, the shark-feeding seems of little concern. However this practice is widespread throughout tropical and subtropical seas of the world and give rise to controversy with little consensus on how it should be managed. Shark feeding is probably one of the most impressive activity tourists can experience under-water. Deliberate and long-term shark feeding is suspected to alter natural behaviour patterns of shark populations, engender dependency and habituation, increasing aggression towards humans by conditioning them to associate humans with food, and to have adverse effects on surrounding communities. On the other hand, tour operators defend the practice as a mean to spread awareness and promote conservation. Despite this controversy, there are few, if any, comprehensive reports that consider the impacts of the shark-feeding while the practice is widespread and growing.
In Moorea Island (French Polynesia), shark-feeding occurs since the 1990s in three localities on the outer slope off the north coast which remain unchanged since the beginning. One locality in the lagoon only feeds stingrays. Shark-feeding implicate several species but mainly the blackfin reef shark (Carcharhinus melanopterus), the grey reef shark (C. amblyrhynchos), the sicklefin lemon shark (Negaprion acutidens).
This study considers the impacts of shark feeding practices in the wild on the behaviour and the ecology of shark populations.
In order to determine biological and ecological aspect of shark populations affected by shark feeding activities in Moorea, it is necessary to study two distinct areas of Moorea Island: one were shark feeding occurs (i.e. the Northern Coast) and another where such activity may not occur (i.e. Southern Coast) and where shark population may not be affected.
The aims are too understand if the shark feeding activity affects the natural behaviour of sharks (i.e. home range, scale of movements, habitat use and residency patterns, density and aggregation, and relatedness in shark populations).
Methods :
To evaluate impact of shark feeding activities on the behaviour of shark populations, we will use 3 different methods in order to reply to the different questions:
1) Acoustic tracking
We will use both remote listening stations (Vemco acoustic receiver VR2) and real time tracking of individuals to compare shark movements in areas where sharks are affected by shark feeding activity and in areas where they are not affected.
2) Underwater observations
Underwater observations permit to quantify shark density in shark feeding site and non feeding sites. For each dive, I note the number of observed sharks to compare density of sharks on the different spots (Number of sharks per dive time). Sharks are identified individually by the photo-identification technique in order to count a shark only once. Two kind of diving are performed: one with food (bait enclosed inside a cage to attract shark without feeding them) and another without. Time before arrival of a shark is recorded in order to compare bait influence on shark in non-feeding and feeding areas.
3) Genetic approach
On sites where sharks aggregate unnaturally because of provisioning diving, naturally social interactions and group structure could be modified. By forming large groups in shark feeding area, this activity can favour intra-specific encounters between resident counterparts favouring a network of related sharks that could form family groups. This could lead sharks to mate with partners from the same family and thus increase locally the inbreeding rate compared with an area where shark feeding does not occur and where sharks would promote gene flow by moving and melting with different populations of unrelated sharks.
The aim is to detect the presence of kin-biased behavioural patterns, testing the hypothesis that blackfin reef sharks patrol with related conspecifics more often than with unrelated ones in “shark feeding” sites compared to “natural” sites.
In order to test this hypothesis, I will use genetic parentage analysis and compare relatedness in different areas of the Island including area affected by shark feeding and other non-affected. This parentage analysis will be performed with microsatellite markers.
