Bryde’s whales in South Brazil Bight: evidence of low genetic diversity and seasonal habitat use

Bryde’s whale (Balaenoptera brydei) is the only non-migratory (resident) baleen whale in Brazil, remaining year-round in the subtropical seas, but are among the least known whales. By combining genetics and spatial analysis, we aim to characterize the genetic diversity and determine the spatiotemporal distribution and habitat-use patterns for the Bryde’s whale population in the South Brazil Bight, in the Santos Basin (23°S to 28°S/40°W to 49°W). During surveys (n = 16) between 2015 and 2018, we recorded 82 Bryde’s whale groups and collected biopsy samples from 13 individuals. Based on our samples, the population of Bryde’s whales presented low genetic diversity. Its distribution varied seasonally, with records occurring mainly in the north of the study area, near Cabo Frio, during warm seasons and in southern waters during cold seasons. The oceanographic dynamics, characterized by diverse frontal systems that enhance productivity on the shelf, likely drive the distribution of the whales, and the seasonal shifts between core areas seem to reflect changes in productivity and prey availability. Our results bring unprecedented information to understand the ecology of Bryde’s whales on the Brazilian coast, and how their distribution and habitats are critically linked with the South Brazil Bight marine environment and its dynamics.