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 Osorio, 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.
Highlights
The southern right whale, Eubalaena australis (Desmoulins, 1822), is a migratory baleen whale that uses southern Brazilian waters as a nursery and breeding ground from June to November (Santos et al, 2001; Groch et al, 2005)
A preliminary study analysing the distribution of southern right whales, using data from sightings from 1987 to 2003, off the southern Brazilian coast, conducted by Espírito Santo et al (2009), demonstrated similar results, confirming that the distribution pattern of southern right whales remained the same
Results show that the sites containing high density of southern right whales are located in front of an area where the shelf break and slope, around 400-800m, around 29°00’00’’S, 49°17’39’’W, are closer to the coast compared to the adjacent regions
Summary
The southern right whale, Eubalaena australis (Desmoulins, 1822), is a migratory baleen whale that uses southern Brazilian waters as a nursery and breeding ground from June to November (Santos et al, 2001; Groch et al, 2005). Previous research regarding the abundance and distribution of southern right whales off the southern Brazilian coast have been conducted as part of photo identification studies through aerial surveys (Groch et al, 2005), stranding events (Greig et al, 2001) data compilation (Santos et al, 2001) and opportunistic observations off the southeastern Brazilian coast (Lodi et al, 1996; Lodi and Rodrigues, 2007). This study had the following objectives: firstly, determining and mapping the distribution patterns of southern right whales along the southern Brazilian coast; secondly, identifying the shelf bathymetry and coastline characteristics where the aggregations occur to investigate influences of this feature in habitat selection
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