Coral reef ecosystems are increasingly threatened by global changes, especially the shorelines where most of human activities are concentrated. These areas serve as nursery areas for several species of sharks and are important in maintaining populations. But how does competition in these restricted areas influence foraging ecology of sharks?
A study in collaboration between Centre de Recherches Insulaires et Observatoire de Environnement (CRIOBE USR3278, PSL Research University: EPHE – CNRS – UPVD) and Florida International University, published in Marine Environmental Research investigated how sharing nursery areas between species influences trophic interactions in juvenile sharks.
We therefore investigated this question using a long-term monitoring program on juvenile sicklefin lemon sharks (Negaprion acutidens) and blacktip reef sharks (Carcharhinus melanopterus) led by CRIOBE over the past 10 years on Moorea Island (French Polynesia) 1, 2. Moorea represents a useful experimental ground to test the influence of competition in juvenile sharks because this island has numerous nurseries sheltering either only one or both of the two species of sharks. In examining stable isotope values of carbon and azote in juvenile sharks, we demonstrated that sharing a nursery with another species led the species to trophic niche partitioning. While they feed on a similar trophic level when they are alone in a nursery, lemon sharks appear to feed on prey with higher trophic level than blacktip reef sharks when they share the same nursery. This partitioning allows the co-existence of both predator species during the first life stages. This plasticity show the capacity of sharks to adapt to competition and more broadly to their environment.
The paper can be found at :
Matich J, Kiska JJ, Mourier J, Planes S & Heithaus MR (2017) Species co-occurrence affects the trophic interactions of two juvenile reef shark species in tropical lagoon nurseries in Moorea (French Polynesia). Marine Environmental Research 127: 84-91.
Previous papers from juvenile shark monitoring in nurseries of Moorea:
Mourier J, Buray N, Schultz JK, Clua E, Planes S (2013) Genetic network and breeding patterns of a sicklefin lemon shark (Negaprion acutidens) population in the Society Islands, French Polynesia. PLoS ONE8(8): e73899.
Mourier J., Planes S (2013) Direct genetic evidence for reproductive philopatry and associated fine-scale migrations in female blacktip reef sharks (Carcharhinus melanopterus) in French Polynesia. Molecular Ecology22 (1): 201-214.