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

This study examined the effects of coastline modification on recruitment patterns of coral reef fishes at Moorea Island (French Polynesia). The fish surveys were conducted at different distances (1, 10, and 30 m) from three natural shorelines (sandy beach, mangrove, muddy herbaceous area) and two engineered shore structures (sea embankment, artificial seawall) over 1 year. In total, 29,187 juveniles were recorded, with 32% of fish on the reefs along sandy beaches (most suitable nursery areas) and only 9% along mangroves. The temporal variation in larval recruitment highlighted that February, March, and April were the best periods for recruitment, with more than 20% of fish recorded, while the minimum (2%) was recorded in July. The fish survey showed that the reefs along each of the five shoreline types were nursery areas for a particular set of species and that many commercial species were specific to the reefs along embankments or sandy beaches. However, the reefs along engineered structures were in bad condition, i.e. less living corals and more macroalgae, in comparison with reefs along unmodified shorelines. Overall, there is an urgent need to better understand how the reefs along natural and artificial shorelines could continue to be nursery areas while facing ongoing climate change and increasing human population living along the coast in the South Pacific Islands.