In April 2019, the famous Marion Dufresne research and supply vessel headed for the Scattered Islands. These five French islands dotted around Madagascar have never had a permanent population. On board the vessel were a dozen biologists and divers who had come to study the fish community in the particularly isolated reefs in the area. The team was banking not only on diving and catching fish, but also on using eDNA found in water samples collected on the surface and at depth to measure biodiversity levels in these unique sites.
The teams were surprised to see a much richer diversity of fish than they had expected in such deep zones.
A system was set up around each island in which six watertight bottles were winched into the water so that samples could be collected at different depths. Using the same procedure, samples were taken at depths of 1,000 meters in submarine canyons, ocean-floor reliefs home to rich ecosystems that we still know little about. While the results of these various samples have yet to be fully analysed, the teams were surprised to see a much richer diversity of fish than they had expected in such deep zones. It remains to be seen exactly which species inhabit these depths; although they do not appear to be particularly hospitable, they undoubtedly provide under-appreciated refuges from the pressure of fishing and climate change..
© Megafauna