Guiana dolphins use mangrove margins as a natural barrier to chase fish prey

Abstract

The behavioral plasticity among and within cetacean species can be driven by their prey sources, local adaptations to environmental features, and/or interactions with human activities. One of the tactics displayed by cetaceans is the barrier feeding, in which individuals or groups herd fish schools against natural and non‐natural barriers to restrict movements of their prey. Coastal odontocetes, for example, are known for using shorelines and underwater slopes to trap their prey. Here, we documented two distinct populations of Guiana dolphin using the mangrove margins as a natural barrier to herd and capture fish. The observations took place in the Cananéia estuary, São Paulo State, southeastern Brazil, and in the Paranaguá estuary, Paraná State, southern Brazil. A total of 63 dolphins over eight encounters were observed performing six different events using mangroves as a natural barrier, summing both study areas. These findings not only expand our understanding of the behavior plasticity of the species but also call attention to the importance of the mangrove ecosystem directly to Guiana dolphins and indirectly to the components of their food web.

Research in a RAMSAR site: The Cananéia-Iguape-Peruíbe estuarine-lagoon complex, Brazil

“…In addition, the occurrence of exotic species and their impacts has been investigated, for instance in cases when the shrimp Litopenaeus vannamei (native to the eastern Pacific) was observed as a bycatch of fishing activities aimed at native species such as the pink shrimp Farfantepenaeus Braga et al paulensis and F. brasiliensis and the white shrimp Litopenaeus schmitti, in several areas of Cananéia, Iguape and Ilha Comprida estuary (Barbieri et al, 2016). Studies on dolphins have been conducted to record the occurrence of the Guiana dolphin (Sotalia guianensis), its local adaptation to environmental features and how human fishing activity can affect its distribution in the CIELC (Godoy et al, 2020;Godoy et al, 2022;Pierry et al, 2023). Ecological studies on abundance, diversity, human impact and environmental drives have been also conducted with marine mysids (Miyashita and Calliari, 2016), gelatinous zooplankton (Cnidaria, Ctenophora, Chaetognatha and Tunicata) (Nogueira Júnior et al, 2019), shrimp such as Xiphopenaeus spp.…”