Mangroves in Small Island Development States in the Pacific: An Overview of a Highly Important and Seriously Threatened Resource

Mangroves are critical resources in small island developing countries in the Pacific where they provide food, a range of products and ecological services that are used by coastal communities. In many of the countries that have mangroves, between 50–80 % of commercial and subsistence fish species used by people spend some part of their life cycle in the mangroves where the detritus and the existing life forms contribute to the productivity of the coastal water that is vital for the habitation of these islands. Mangroves also protect the shorelines and are harvested for timber and non-timber products such as charcoal, dye and medicine. Ironically, this important resource is increasingly cleared in large amounts to allow for infrastructure development, agriculture, fish farming, hotel sites, industrial areas and dumps. Most small island countries in the Pacific Islands do not have any effective management plans for their mangrove forests, which are now under serious threat because of their increasing alteration to accommodate other uses. In addition, the changes in climate and sea levels and their impacts and how these are being addressed and attended to at different levels in the Pacific Islands will be discussed to show the attempts at all levels to accommodate the changing conditions. Many of these countries still cannot determine the factors that influence the sustainability of their mangroves which normally come under the responsibility of ministries or departments of forestry, fisheries, natural resources, environment and lands. It is common to have jurisdictional overlaps and conflicting sectoral policies. This overview will present the current state of mangroves and some of the issues that characterise their use in the Pacific Islands, the threats they face and the management arrangements that are in place. The chapter will also illustrate the roles of the customary and traditional owners of the resource and governments at the local, national and regional levels and the challenges that mangrove management must overcome in order to ensure the integrity and health of this habitat that is fundamental to human wellbeing

Effects of Coastline Modification on Coral Reef Fish Nurseries (Moorea, French Polynesia)

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Marine biodiversity of a pristine coral reef in French Polynesia

International audienceUnderstanding 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

Colour differentiation in a coral reef fish throughout ontogeny: habitat background and flexibility

Colour polymorphism is widespread in animals but, in contrast to other types of polymorphism, has been little explored during ontogeny. Among coral reef fish, the surge damselfish Chrysiptera leucopoma settles in the larval stage as a yellow morph, whereas 2 colour morphs (yellow and brown) are apparent in adults at Rangiroa Atoll, French Polynesia. To understand this dimorphism, we tested, under controlled conditions, the hypotheses that: (1) environmental cues (habitat background and conspecific density) play important roles in morph differentiation during ontogeny and (2) morph colouration is reversible. Our first experiment showed that a dark habitat background induced the formation of the brown morph, while C. leucopoma larvae kept their yellow morph when placed in aquaria with a bright habitat background. Colour change from yellow to brown also occurred within the bright habitat, but only at high conspecific densities. Our second experiment showed that colour change was reversible within 15 d post-settlement, but not at the adult stage. Overall, our results highlighted that the studied polymorphism may be environmentally induced and reversible during the first post-settlement days of this coral reef fish

Importance of intertidal seagrass beds as nursery area for coral reef fish juveniles (Mayotte, Indian Ocean)

International audienceThe present study highlights the importance of intertidal seagrass beds as nursery areas for coral reef fish juveniles along four sites (Mtsoubatsou, Sohoa, Boueni, Ngouja) on the western coast of Mayotte Island. The results collected by underwater visual census from November 2012 to January 2013 showed that mean total fish density between adults and juveniles varied significantly at each site, with juveniles always being more abundant in seagrass beds than adults. Of the total fish assemblages sampled in seagrass beds, 73% were juveniles and few adults of large species were observed. Overall, our study highlights the important functional role of intertidal seagrass beds for fish assemblages, as they are the primary habitat for the juveniles of many fish species on Mayotte reefs. Seagrass beds, however, are very vulnerable ecosystems and are decreasing worldwide. Therefore it is of primary importance to protect seagrass beds within the Indo-Pacific

Long term relationship between farming damselfish, predators, competitors and benthic habitat on coral reefs of Moorea Island

International audienceAbstract Understanding the processes that shape biodiversity is essential for effective environmental management. Across the world’s coral reefs, algal farming damselfish ( Stegastes sp.) modify the surrounding benthic community through their creation of algae “farms”. Using a long-term monitoring dataset (2005–2019) from Moorea Island, French Polynesia, we investigated whether the density of dusky damselfish ( Stegastes nigricans ) is associated with benthic habitat composition, the density of predators and/or competitors, and whether the survey area was inside or outside of a Marine Protected Area (MPA). We found no evidence that benthic cover or number of competitors were associated with dusky damselfish densities, both inside and outside MPAs. In contrast, fluctuations in dusky damselfish densities were negatively associated with the density of predators (e.g. Serranidae, Muraenidae and Scorpaenidae) in the preceding year in non-MPA areas, and both within and outside of MPAs when predator densities were high (2005–2010). These results suggest that healthy predator populations may be important for regulating the abundances of keystone species, such as algal farming damselfish, especially when predator densities are high

Characterization of the different sound sources within the soundscape of coastline reef habitats (Bora Bora, French Polynesia)

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Local perceptions of socio-ecological drivers and effects of coastal armoring: the case of Moorea, French Polynesia

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Assessment of ecological status of the lagoon of Bora-Bora Island (French Polynesia)

International audienceIn the South Pacific, an important island has been forgotten and neglected from monitoring and research programs on marine biodiversity: Bora-Bora, often called the ‘Pearl of the Pacific’. To fill this gap in our knowledge, we have analyzed the only two datasets available to date on the biodiversity of Bora-Bora’s reefs: Reef Checks’ program, conducted on 18 sites inside the lagoon in 2006 and 2018; and Biodiversity’s monitoring program, conducted on 31 lagoon sites in 2019. Both monitoring programs showed that the corals in Bora-Bora lagoon are in good health. The living coral cover has been stable on all recorded geomorphological zones between 2006 and 2019. In contrast, there was a strong decrease in the density of all macro-invertebrate species recorded (i.e. giant clams, sea-urchins, sea-cucumbers, sea-snails). For giant clams, three human-related causes of extraction were identified: collecting activities of tourists, local inhabitants and occasional major predation by large groups of people visiting from other islands for local festivities. Lastly, both monitoring programs showed that all commercial families (i.e. Acanthuridae, Scaridae, Serranidae) increased in density over time. This may be because the larval recruitment of fish seems to be sufficient to offset the loss of adults from local fishing. Overall, our monitoring programs, conducted on coral, macro-invertebrates and fish, suggest that the luxury tourism industry developed at Bora-Bora contributed to the maximization of the economic and social benefits of coral reefs while preserving Bora-Bora’s natural sites, ecosystems and the socio-cultural balance

Distribution patterns of ocellated eagle rays, Aetobatus ocellatus, along two sites in Moorea Island, French Polynesia

Elasmobranchs are critical to tourism industries worldwide. In French Polynesia, where ecotourism is the second most important industry, little is known about the spatiotemporal distribution of eagle rays. This study represents the first investigation into habitat use and behaviour of ocellated eagle rays (Aetobatus ocellatus) in French Polynesia focused on two sites with different levels of anthropogenic noise. Environmental variables and biological data were recorded over a one-year period to explore the distribution patterns of 113 eagle rays identified at these sites. Results revealed distinct patterns in-habitat use between the two sites, with the eagle ray population structured according to ontogenetic stage. Young rays preferred the site with lower levels of noise pollution, where they foraged at the end of the day. Adult eagle rays gathered in the mornings at the louder site, where the only noticeable activity was group swimming. Overall, our results could help conservation initiatives to manage this important species in French Polynesia, and potentially other coral reef areas, especially in the context of rising human impacts on the environment