Marine biodiversity of a pristine coral reef in French Polynesia

Abstract

Understanding the natural state of coral reefs is paramount to evaluate the response of these ecosystems to local and global human impacts as well as management and conservation strategies. In French Polynesia, some islands are still pristine or uninhabited, such as Tupai atoll. Tupai has been uninhabited, with access to the lagoon prohibited since 2010. However, fishers from nearby islands often take from the outer reef slope at Tupai. Our marine biodiversity survey (coral, macro-invertebrates, and fish) conducted in 2019 highlighted a low density of commercial fish species and top-predators on the outer slope in comparison to the lagoon, where the top-predators represented 16% (of the density) of functional trophic groups. Our surveys also showed a high living coral cover (46%) on the outer slope of Tupai, perhaps due to the absence of both touristic sub-aquatic activities and local pollution from private and commercial activities. Overall, this initial scientific assessment of Tupai has granted an understanding of the spatial patterns of coral, macro-invertebrates, and fish assemblages in the absence of human impacts (i.e., in the lagoon), representing an ecological baseline that could inform conservation management strategies to ensure the preservation of coral reef ecosystem.

Spatial and temporal analysis of juvenile blacktip reef shark (Carcharhinus melanopterus) demographies identifies critical habitats

“…Moorea is part of the largest shark sanctuary on a global scale, and in French Polynesia all shark species are protected. Nonetheless, it is likely that sharks are being poached in remote and uninhabited islands and atolls of French Polynesia (42 of the 118 coral islands are still uninhabited; Lecchini et al ., 2021) as maintaining a surveillance of such a large sanctuary is likely to present flaws. The presence of human populations increases surveillance, restricting poaching activities as sharks have economical (sharks are a lucrative source of tourism with several dedicated shark observation areas inside and outside the lagoon) (Esposito et al ., 2022; Rieucau et al ., 2018) and cultural values (Skubel et al ., 2019).…”

“…Reef shark abundance has declined tremendously over the last decades across all coral reefs (Camhi et al 2009;MacNeil et al, 2020;Sherman et al, 2023;White et al, 2017). Assessing reef shark population abundance at recovery, increase or decline is often greatly challenging because we lack spatial and temporal monitoring data on their population dynamics (Latour & Gartland, 2020). In this study, a unique database provided time series of a juvenile reef shark population monitoring program spanning nine years and ten sampling sites around Moorea Island (French Polynesia).…”

“…Yet despite the current conservation measures adopted by several countries worldwide to mitigate these anthropogenic effects, many reef shark species are still listed as vulnerable, near threatened, or threatened on the IUCN Red List for endangered species (MacNeil et al, 2020;White et al, 2017). Because all coral reef ecosystems are affected by human activities in one way or another, we have no baseline for what a healthy reef shark population should look like (Ferretti et al, 2018;Hughes et al, 2003;Lecchini et al, 2021). Moreover, geopolitical boundaries defining protected coral reef ecosystems do not necessarily have the highest shark densities (MacNeil et al, 2020;Ward-Paige & Worm, 2017).…”

“…What is more, because all coral reef ecosystems are affected by human activities in one way or another, we have no baseline for what a healthy reef shark population should look like (Ferretti et al, 2018;Hughes et al, 2003;Lecchini et al, 2021). Moreover, geopolitical boundaries defining protected coral reef ecosystems do not necessarily have the highest shark densities (MacNeil et al, 2020;Ward-Paige & Worm, 2017).…”