Distribution of tursiops truncatus in Southeastern Brazil: A modeling approach for summer sampling

Abstract

Distribution modeling is a relatively new tool to study cetaceans distribution and is used to understand their relationships with the habitat, which in turn, can be used for several purposes. This is the first attempt to model Tursiops truncatus distribution in South- Atlantic Ocean. A Generalized Additive Model (GAM) was developed to investigate how the distribution of T. truncatus in Cabo Frio, Brazil, during summer (December to February) is influenced by depth, distance to coast, slope,. Furthermore, we tested the efficiency of a model with number of groups (total occurrence) as response variable compared to a presence-absence data. Our results indicated that total occurrence model was more robust than presence-absence. Dolphins were found regarding to depth most frequently around 30-60 m and decreasing in more profound depths. Dolphins occurrence decreased as distance to coast increased. Our results show that Cabo Frio is an important site for T. truncatus since it may provides feeding resources and a safe place against predators. However the fast development of human activities may threaten this important area and therefore this dolphin species in Brazilian waters. © 2013 ABECO.