Habitat modelling of the southern right whale (Eubalaena australis) in the breeding area of southern Brazil

Southern right whales migrate seasonally between breeding and feeding grounds, and the southern coast of Brazil is one of their key breeding areas in the Atlantic Ocean. Recent observations suggest a notable decline in whale occurrences in this region since 2015. Since 2015, the occurrence and abundance patterns of right whales in Brazil have changed. To better understand past habitat use and establish a baseline for comparing future distribution trends, we modelled whale distribution using data from aerial surveys conducted between 2003 and 2012, covering the area from Palhoça, Santa Caterina to Torres, Rio Grande do Sul, Brazil. Generalized additive models were employed to assess the influence of environmental and spatio-temporal variables on whale distribution. Our results revealed that whale abundance follows a four-year cycle, which differs from the established three-year reproductive cycle. Higher whale numbers were observed in shallow areas (<10 metres deep) with gentle slopes and near river mouths. The Ribanceira/Ibiraquera region exhibits the highest concentration of whales. These findings provide critical insights into historical habitat preferences and serve as a valuable reference point for evaluating ongoing and future changes in the species’ spatial distribution along the Brazilian coast, thereby supporting the development of targeted conservation strategies and more effective management plans for southern right whales in the region.