Analysis of the distribution patterns of southern right whale off the southern Brazilian coast

Abstract

The southern right whale, Eubalaena australis, is a migratory baleen whale that uses southern Brazilian waters as a nursery and breeding ground from June to November. This study aims to determine the distribution patterns and main aggregation sites of southern right whales off the southern Brazilian coast from around Santa Catarina Island to Osório, and to investigate the population distribution according to the coastline and bathymetric features. The methods consisted in obtaining geographical coordinates for each individual, sighted through helicopter expeditions over a transect along the coastline, conducted once a year in September, from 2001 to 2010. This data was used to generate a density estimate surface map of southern right whales using the Kernel Density Estimator. Additionally, a digital bathymetry was overlaid to the density estimate map. The results pointed out a region of high density estimate of southern right whales, located from 28°12’22”S, 48°39’25”W to 28°33’58”S 48°47’19”W, respectively, from Imbituba to Santa Marta Cape. The largest aggregations were observed where the shelf declivity is higher, as a result from the bathymetric lines of 10 m and 40 m being closer to each other, and where the coastline shows great amount of bays. We highlight the importance of monitoring the southern right whales distribution patterns observed in this study, aiming to identify possible habitat changes that can be indicative of disturbances on their populations.

Key words: Eubalaena australis, reproductive grounds, Kernel Density Estimator.