Direct genetic evidence for reproductive philopatry and associated fine-scale migrations in female blacktip reef sharks (Carcharhinus melanopterus) in French Polynesia

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Here is my new paper on the reproductive migrations of females blacktip reef sharks to their nursery area inferred from parentage analysis.

Mourier, J.& Planes, S. (in press). Direct genetic evidence for reproductive philopatry and associated fine-scale migrations in female blacktip reef sharks (Carcharhinus melanopterus) in French Polynesia. Molecular Ecology. Doi: 10.1111/mec.12103

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Figure 1: Migrations of female blacktip reef sharks from their site they are attached to, to their nursery area in Moorea. Note that some are going to the same nursery on multiple years to give birth. This was demontrated using genetic parentage analysis that assigned juveniles back to their parents within the population.

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Figure 2: Reproductive migrations between Moorea and Tetiaroa, 2 islands separated by about 50 km and deep water (>2000 m).

Figure 3: An example of the monitoring of a female’s pregnancy. Its pup was found and sampled December 2009 in one of the nursery.

Abstract

Conservation of top predators has been emphasized as essential in an ecosystem due to their role in trophic chain regulation. Optimizing conservation strategies for these endangered marine top predators requires direct estimates of breeding patterns and connectivity as these are essential to understanding the population dynamics. There have been some attempts to investigate breeding patterns of reef sharks from litter reconstruction using molecular analyses. However, direct fine-scale migrations of female sharks for parturition as well as connectivity at a medium scale like between islands remain mostly unknown. We used microsatellite DNA markers and a likelihood-based parentage analysis to determine breeding patterns of female blacktip reef sharks in Moorea (Society Islands, French Polynesia). Most females gave birth at their home island but some migrated to specific nursery areas outside the area they are attached to, sometimes going to another island 50 km away across deep ocean. Our analysis also revealed that females migrated to the same nursery for every birthing event. Many offspring showed a high level of inbreeding indicating an overall reduced population size, restricted movements and dispersal, or specific mating behaviour. Females represent the vectors that transport the genes at nursery grounds, and their fidelity should thus define reproductive units. As females seem to be philopatric, males could be the ones dispersing genes between populations. These results highlight the need to conserve coastal zones where female reef sharks seem to exhibit philopatry during the breeding season.

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