Short-term responses and potential impact of tourism activities on dusky dolphins, in Golfo Nuevo, Argentina

SILVANA L. DANS; ENRIQUE A. CRESPO; SUSANA N. PEDRAZA; MARIANA DEGRATI; GRISELDA V. GARAFFO

Liege

Congreso; 16th EUROPEAN CETACEAN SOCIETY CONFERENCE; 2002

Dusky dolphins became a target for tourism activities off Patagonian coast, Argentina. Several low-scale studies have been conducted during the last  year in order to assess natural patterns in occurrence and behaviour and to evaluate short-term responses of dusky dolphins to boats. First, we analysed which is the main activity in which dolphins are engaged when approached, second in which circumstances dolphins do change or not their behaviour, and at last, how much time they need to resume the initial conditions. Ship-based surveys were done in summer-fall, 2001, through random transects by a research boat and by tourism trips. When a group of dolphins was detected, the predominant activity was assigned before the boat approached the dolphins, at 200mts or more, and it was reassigned when the research boat was at 100mts and the commercial boat was at 50mts or less. Group size and composition were recorded at this moment and the activity was recorded for each 2min interval thereafter. Among seventy-four groups, the main activity before the commercial vessel approached was feeding, followed by travelling and socialising, while feeding, travelling and resting were the main categories from the research vessel. Feeding decreased and travelling increased after the approach. Feeding is the most affected activity (c2=14.44; p<0.0007) and there were no differences between boats (c2=0.07; p>0.05). Mother with calves seemed to be more susceptible. Time spent feeding decreased during the first 48min of the encounter (c2=8.55; p<0.03). By observing dolphins from the research boat, feeding decreased and travelling increased while the commercial boat was close to the dolphins. Once the commercial boat abandoned dolphins, travelling decreased and feeding slightly increased, although differences were not significant. The time that the boat stays with the dolphins as well as the effect of the boat on the aggregation of dolphins may preclude longer feeding bouts.