Possible collapse of reef shark populations in remote coral reef ecosystems in the Coral Sea (Western Pacific)
The decline of meso-predators such as reef sharks is a concern as such species can have important ecological roles in maintaining reef ecosystem resilience. Two field trips conducted in August 2010 and November 2011 to the Chesterfield archipelago (Coral Sea) allowed us to assess the abundances and average sizes of medium-bodied Carcharhinidae with a specific focus on grey reef shark (Carcharhinus amblyrhynchos), through fishing (46 hours of accumulated effort) and underwater visual censuses (25 hours of accumulated effort). We found low abundance and small average total length (TL) for all reef shark species, and in the case of the grey reef shark, an average abundance of 2.1 individuals/dive with the majority of animals less than 110 cm TL. We compared our findings with historical data and, given our low sampling effort, we so far hypothesise that a general strong decline in the reef shark populations may have occurred in this area, probably due to recent overfishing. The enforcement of conservation measures is strongly recommended among these remote reefs as well as complementary studies for confirming this hypothesis.