Habitat Use And Preferences Of Tucuxi Marine Dolphins In Paraty Bay (Rio De Janeiro, Brazil)

By Liliane Lodi

The marine tucuxi dolphin or gray dolphin, Sotalia fluviatilis, is endemic along the tropical and subtropical Atlantic coastlines of South and Central America and is perhaps the cetacean most affected by human activities, mainly incidental captures in Brazil, after the franciscana, Pontoporia blainvillei. Since it has coastal habits, S. fluviatilis is a vulnerable species and it is mentioned in several lists of threatened animals.

Marine Tucuxi Dolphins, Paraty Bay, Brazil
Photo by Liliane Lodi

A number of factors raise conservation concerns about this species: 1) its restricted distribution; 2) its apparent vulnerability to incidental captures and lack of reliable estimates of total bycatches; 3) the lack of information about its abundance, and 4) the vulnerability of its coastal/estuarine habitats to degradation by pollutants, boat traffic and overfishing.

With the support of Cetacean Society International, the Dolphins Project ("Projeto Golfinhos") was begun in October 2000, a study with marine tucuxi dolphin that inhabits the Paraty Bay (23° 13'S 44° 42'W; 23° 02'S 44° 35'W) region on the south of Rio de Janeiro State, Brazil. This study (which has a duration of one year) will examine environmental and behavioral determinants of the habitat use and preferences of the marine tucuxi dolphin in Paraty Bay.

Overfishing and predatory fisheries have been causing serious impacts on the marine environment in Paraty Bay in the last three decades. Fish stocks have been decreasing year after year, harming or suspending economic activities proven to be profitable in the past, like sardine, shark, and shrimp fisheries, among others. It is possible that, in close future, those impacts may cause disastrous damage to the marine ecosystem of Paraty Bay. Since availability and variability of prey may regulate movements of the majority of cetacean species, the decline in fish stocks may be already affecting the occurrence and distribution of cetaceans in Paraty Bay.

An adequate identification of key habitats within a population's home range and core areas where biologically and socially important behaviors concentrate is important for understanding the species' ecology and crucial for the conservation and management of any wild animal population.

The results obtained in this study will provide the basis for identifying marine tucuxi dolphin critical habitats in Paraty Bay, which should be considered an integrated coastal zone management. Furthermore, this work represents an important step towards understanding the dependence of these vulnerable animals on the restricted, shallow-water, inshore marine environment and, as such, should be valuable for other areas where there is little knowledge of marine tucuxi dolphins and their ecological requirements.

The Marine Tucuxi Dolphin Area of Environmental Protection of Paraty Bay will be proposed by the Dolphins Project in 2002 to the Municipal Town Hall of Paraty.

For more information see: http://www.paraty.com.br/golfinho.htm