How do Guiana dolphin (Sotalia guianensis), from the Cananéia estuary in State of São Paulo, use cerco-fixo fish traps in their fishing activities?

Abstract

In the Cananéia estuary there is a rare positive interaction between a cetacean and a type of fishing activity. In this region the Guiana dolphin (Sotalia guianensis) uses cerco-fixo fish traps to corner shoals and reduce the escape routes of their prey, and in doing this increase their capture efficiency. The object of this study was to evaluate, by means of a quantitative analysis, how the Guiana dolphin uses the cerco-fixo fish trap in their fishing activities. Their behaviors were quantified separately according to a group structure, so as to also verify how their behaviors vary according to the number of individuals involved in the strategy. This approach serves to improve understanding about what the role of the trap in fishing strategies is and how its use, such as using it as a shield to block the shoals, influences the frequency of behaviors executed during fishing activities.