Underwater robots provide similar fish biodiversity assessments as divers on coral reefs

Coral reefs are under increasing threat, and the loss of reef-associated fishes providing valuable ecosystem services is accelerating. The monitoring such rapid changes has become a challenge for ecologists ecosystems managers using traditional approaches like scuba divers performing underwater visual censuses (UVC) or diver operated video recording (DOV). However, use small, low-cost robots could help tackle monitoring, provided that they perform at least as well diver-based methods. To address this question, tropical fish assemblages from 13 fringing around Mayotte Island (Indian Ocean) were monitored along 50 m-long transects stereo videos recorded by semi-autonomous vehicle (SAUV) (Diver Operated Video system, DOV). Differences between methods tested complementary assemblage metrics (species richness, total biomass, density, Shannon diversity Pielou evenness) number size nine targeted species. SAUV on average 35% higher biomass than DOV which in turn 12% species richness. Biomass differences found to be due larger DOV, potential marker human-related avoidance behaviour. This study demonstrates provides accurate coral reef biodiversity compared procedures. Given their ability conduct high frequency, 100 m depth range moderate cost, promising tool ecosystems.