Shallow‐water habitat use and population parameters of rough‐toothed dolphins, Steno bredanensis ( G. Cuvier in Lesson, 1828) in southeastern Brazil

Abstract

The rough‐toothed dolphin ( Steno bredanensis ) is a poorly known species along its distribution especially in the Southern Hemisphere where data on habitat use and population parameters are scarce. Boat‐based surveys were conducted from 2009 to 2017 in a shallow water environment in southeastern Brazil. During focal‐group observations, S. bredanensis was more commonly found in mean depths of 22 m with varying group size and composition. Generalized additive models showed that group size was influenced by environmental variables such as sea surface and bottom temperatures, depth, and season. Photo‐identification effort allowed us to catalogue 173 well‐distinct marked individuals. Estimates of population parameters showed high and constant survival (Φ = 0.99) corroborating site fidelity but time varying capture probabilities ( p = .03–.71). An open population model also indicated a small abundance estimate ( Nt = 218) of S. bredanensis in the study area, improving knowledge for this species in shallow water environments of the southwestern Atlantic Ocean.

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