Shifts in coral reef fish populations linked to human pressure and tourism activities revealed by COVID-19 restrictions

Abstract Throughout the world, anthropogenic pressure on natural ecosystems is intensifying notably through urbanisation, economic development, and tourism. Coral reef organisms worldwide have become exposed to stressors related to tourism activities. To reveal the impact of human activities, the COVID-19-related social restrictions put in place since 2020 can be used. In French Polynesia, from February to December 2021, there was a series of restrictions of local activities as well as bans of international tourism. These led to variations in the intensity of tourism activities. Here, we aim to determine the consequences of the rapidly changing activity restrictions on the species richness and density of juvenile and adult fish of all species and of harvested species in the lagoon of Bora-Bora (French Polynesia) across sites dedicated to tourism activities, affected by boat traffic, or with low traffic and tourism. Underwater visual surveys demonstrated that the density and species richness of juvenile and adult fish of all species and of harvested species were highest during total lockdowns and lowest when all activities were authorised. Adult and juvenile fish density and species richness increased the most during periods without tourism on sites usually visited by tourists. Fish density and diversity were lowest on sites affected by boat traffic regardless of restriction level, indicating a strong influence of human presence on fish sightings in the lagoon. Overall, COVID-19-related restrictions highlight that human activities are major drivers of fish abundance and species richness on Bora-Bora, calling for a sustainable planning of the lagoon usage.