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.

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

“…Parameters (Table 1) from the rough-toothed dolphin population from Rio de Janeiro state (SE Brazil) were used for all three populations since no data was available for the other two populations. 24 Data of model species, such as the bottlenose dolphin, were used as a proxy when the information needed was not available for the studied species since both belong to the Delphinidae family and aspects of the ecology of bottlenose dolphins are well described in the literature 39,40 (Supporting Information).…”

“…Hence, the original SE population parameters were chosen to compose the IBM framework as to reflect the unique dynamics of this coastal population. 24 As the model only considers female individuals in the population, a male/female conversion ratio of 1.8 was calculated based on the SE population and applied to both S and OCS/S populations because of the low number of females (Table S1, Supporting Information).…”

“…The rough-toothed dolphin (Steno bredanensis) is classified as oceanic, inhabiting deep waters from warm temperate and tropical regions of the Atlantic, Pacific, and Indian oceans. 23 However, a close association with coastal, warm, and shallow waters was described for a population in the Southwestern Atlantic Ocean (SWAO), 24 as well as the use of the inner continental shelf for foraging, 25 underscoring the exposure of the species to threats inherent to habitats that suffer from multiple anthropogenic pressures. 20,25 Hence, there is an increasing concern about the distinctive coastal habit in this region.…”

“…20,25 Hence, there is an increasing concern about the distinctive coastal habit in this region. 24,25 Information regarding the population structure of rough-toothed dolphins and contamination levels is of utmost importance for species maintenance. Therefore, accessing the profile of POPs in rough-toothed dolphins is necessary not only to quantify the risk of impact of such pollutants on the exposed populations but also to distinguish ecological populations based on their differences in usage of area and/ or prey consumption.…”

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

“…Indeed, the first report of such parameters was recently published by Carvalho and collaborators (2020) 15…”