This paper reports on aerial surveys conducted to estimate the relative abundance and trend in growth of the southern right whale (Eubalaena australis) population from Península Valdés. The number of whales counted tripled from 1999 to 2016. We modeled the number of whales, the number of calves, the number of solitary individuals and the number of individuals in breeding groups using as predictive variables the year, Julian day, and Julian day2 by means of generalized linear models. The rate of increase decreased from near 7% in 2007 to 0.06% and 2.30% for total number of whales and number of calves, respectively for 2016. Trends in the rates of increase for total number of whales and number of calves were negative (−0.732% and −0.376%, respectively). The habitat use of the whales changed along the years, with mothers and calves using more heavily the near‐shore strip, resulting in a decreasing trend for solitary individuals and breeding groups in near‐shore waters. We conclude that whales are still increasing their abundance, while the rate of increase is decreasing. Differences in the rates of increase of the group types and changes in habitat use are thought to be the consequence of a density‐dependence process.

Dolphin watching is a relatively newly developed tourist activity. Although it is assumed to contribute to the conservation of marine ecosystems, its long-term adverse effects are still unknown. The present work aims to assess the impact of tour vessels on the behavior pattern of dusky dolphins displaying diurnal and cooperative feeding. We evaluated potential bias of commercial vessels to specific activities, short-term responses of dolphins to vessel approach, and longer-term effects of these changes, particularly on the activity budget and the time dolphins need to resume an activity. Several field experiments were carried out in which dolphins were approached by a research vessel or by commercial vessels. Group tracking was also made from a research vessel. Behavioral sequences were modeled by stochastic matrix models. Activity budget and time to return to an activity were obtained from matrix properties. Commercial trips found mostly feeding groups. Feeding showed the highest rate of change at the moment of vessel approach, and commercial vessels had an effect on the direction of change. Over the longer term, feeding and socializing time budgets decreased when commercial vessels were present. The time to return to feeding as well as the time it took for a group of dolphins to feed increased in the presence of commercial vessels. Dusky dolphins in South Atlantic waters feed during the day on patchily distributed prey. Our study demonstrates that boat presence negatively affects the longer-term feeding efficiency of dusky dolphins.

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