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Abstract

This study took place at the Guaratuba Bay area, south of Paraná State, Southern Brazil. The study's main objective was to gether informations on the occurrence of marine mammals, and their interspecific interactions. Interspecific interactions involved: a) Two species of dolphins, S. f. guianensis and T. truncatus, when the animals are apparently engaged in fishing activity. This interaction seems to be positive for both species of dolphins, but was observed on only one occasion; b) Interactions between dolphins and different species of birds (Ciconiiformes Ardea cocoi, and Pelecaniformes Sula leucogaster). During the fishing activities, the dolphins frequently swim around the shoals and fish constantly jumping out of the sea, becoming easy prey for the birds alone. It appears to be very positive for the birds, but a matter of indifference to the dolphins; c) Interactions between men and dolphins. It occurs when the dolphins swim around the shoals, thus helping the men to locate fish. On the other hand, when throwing their nets, fishermen lead the fish towards the dolphins, making their catch easier. This interaction is positive for both men and dolphins involved. Nevertheless, there are intentional negative interactions, such as when the men sail their small boats towards the dolphins; d) Negative interactions, which takes place between men and three species of pinnipeds, Otaria flavescens, Arctocephalus tropicalis and A. australis, found in the area particulary in the winter, especially near the beaches but are rarely found in the river areas. These pinnipeds are taken to places were conditions for their maintenance are inadequeate, and usualy they die. Sometimes they are killed, not always accidentally by the local people.