The behavior of Sotalia guianensis (Van Bénéden) in Pernambuco coastal waters, Brazil, and a further analysis of its reaction to boat traffic

Abstract

There is still little knowledge about the behavior of the estuarine dolphins and also the way they react to the presence of different types of vessels. The aim of the present study was twofold: to investigate the behavior of estuarine dolphins in four locations in Pernambuco, Brazil, and also their reaction to the presence of common types of nautical crafts. The data of this study resulted from 48 fieldtrips to each of the four localities studied (ports of Recife and Suape, and beaches of Bairro Novo and Piedade), thus totaling 192 days of observations, with approximately 380 hours of actual sampling. Ten types of behavioral activities were counted for Bairro Novo beach and the port areas, but only four for Piedade beach. The greatest flows of boats were recorded in the port of Recife. Fishing boats were the commonest type in the port area of Recife and Bairro Novo beach, while tourist vessels predominated in the port of Suape and Piedade beach. During the observations of encounters between these boats and the estuarine dolphins, neutral reactions predominated for all the vessel types studied. The same type of reaction predominated when the distances at which the interactions between the animals and vessels occurred were correlated.

Surface patterns of Sotalia guianensis (Cetacea: Delphinidae) in the presence of boats in Port of Malhado, Ilheus, Bahia, Brazil

“…The direction of vessel traffic must also be considered when studying interactions with cetaceans. In this study, as similarly reported by Araújo et al (2008), the vessels only passed through the area and spent a short time interacting with the dolphins. The distance from boats did not interfere in the surfacing pattern of the dolphins.…”

“…In contrast, Araújo et al (2008) observed a predominance of neutral reactions to all types of boats. These authors suggested that the reactions were neutral because the speed and direction of the boats were constant.…”

“…Distance categories were created following Araújo et al (2008). Thus, comparisons between port systems were possible.…”

“…Research on the interaction between S. guianensis and boats, has been performed along the Brazilian coast (Santos-Jr. et al, 2006;Valle & Melo, 2006;Pereira et al, 2007;Araújo et al, 2008;Carrera et al, 2008;Filla et al, 2008;Tosi & Ferreira, 2008).…”

Assessing population parameters and trends of Guiana dolphins (Sotalia guianensis): An eight‐year mark‐recapture study

“…Guiana dolphin populations are frequently exposed to human activities because they inhabit coastal areas (Borobia et al 1991). Mortality due to accidental ( e.g ., Di Beneditto 2003) and intentional catches (Sholl et al 2008), boat strikes ( e.g ., Van Bressem et al 2007), behavioral disturbances due to boat traffic ( e.g ., Araújo et al 2008), skin diseases ( e.g ., Van Bressen et al 2009), and high levels of persistent contaminants in tissues ( e.g ., Yogui et al 2003) are known threats to this species. Effective monitoring efforts that provide robust estimates of a set of population parameters are therefore a necessity.…”