Identifying primary drivers of reef elasmobranch relative abundance and distribution across a suite of biotic and abiotic gradients

The Exclusive Economic Zone of French Polynesia covers an area half the size of Europe, contains 5% of the world’s living coral biomass, and has relatively intact shark populations. Indeed, reef-associated elasmobranchs... [ view full abstract ]

The Exclusive Economic Zone of French Polynesia covers an area half the size of Europe, contains 5% of the world’s living coral biomass, and has relatively intact shark populations. Indeed, reef-associated elasmobranchs have not been subjected to commercial fisheries and in 2012 the entire EEZ was declared a shark sanctuary. Within French Polynesia there are considerable gradients of human population density, cultural background, and socio-economics coupled with natural gradients of island size and type (e.g. high islands vs atolls), reef structure, productivity and abiotic factors. Therefore, during the Global FinPrint project, we used French Polynesia as a model for understanding how the abundance and diversity of reef-associated sharks and rays varies across natural and anthropogenic gradients in the absence of commercial fishing. From 2017-2018, we conducted baited remote underwater videos surveys (n=1,750 camera deployments in forereef habitats) across 35 islands and atolls; complemented by 300 semi-structured social science interviews from a variety of ocean-users, particularly to assess the extent of cultural variations in attitude to sharks and overall awareness of the regulations in place protecting them. A Generalized Linear Model was used to assess the relative importance of natural and anthropogenic factors in the spatial variation of elasmobranch species richness and relative abundance. Abundance was greatest in areas of higher productivity and species composition varied spatially.  We found that although there was relatively little reported pressure on shark populations, knowledge about the shark sanctuary and shark protections were comparatively limited. Better communication about the sanctuary could help increase compliance