Study and conservation of the Guiana Dolphin (Sotalia guianensis) (Van Bénéden, 1864) in French Guiana

The Guiana dolphin (Sotalia guianensis) occurs in warm and shallow waters of the Atlantic Ocean and the Caribbean Sea, from southern Brazil to Honduras, including estuarine and freshwater habitats such as Maracaibo Lake (Venezuela), and the Orinoco River. In 2018, the Guiana dolphin was reclassified from Data Deficient to Near Threatened on the global IUCN Red List. Nevertheless, the conservation status identified by national and regional Red Lists is even more alarming. In French Guiana, for example, the species is classified as Endangered based on strong pressures such as bycatch. In this region, the Guiana dolphin inhabits river mouths and coastal waters where most anthropogenic activities occur. Better knowledge of the biology and ecology is needed in French Guiana to help inform effective conservation actions. Here, we present ongoing studies to map the distribution of Guiana dolphins along the French Guiana coast and estimate abundance in a hotspot area. Aerial survey campaigns were conducted during the dry season in 2013, 2014, 2015, and 2019. Eight flights were conducted and 146 dolphins belonging to 39 groups were observed. Boat-based line-transect surveys were also conducted in the coastal waters of Cayenne in 2017 and 2018. Twenty-one survey trips were conducted covering 999.06 km. Three hundred and eighty-two dolphins belonging to 63 groups were observed. The total abundance in the Cayenne area was estimated at 128 dolphins (% CV = 30.92; CI (95%) = 70-235) with a density of 0.80 ind./km² (% CV = 30.92; CI (95%) = 0.44-1.47). Additionally, a descriptive analysis was performed on stranding data collected in French Guiana between 2014 and 2020 to identify the major cause of death and seasonality in the stranding events. In total, 43 dolphins were found, especially on the beaches of Rémire-Montjoly, Cayenne, and Kourou: bycatch was the major identifiable cause of death. We recommend a local conservation strategy and actions to be undertaken in the short- and medium-term to address different issues: knowledge, threats, conservation, and cooperation