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Guiana Dolphin population viabilityin a South Atlantic Estuary

Changes in the habitat quality and coastal waters during the past decades are significant and wildlife have been affected by human activities. Coastal cetaceans are constantly exposed to bycatch, boat collisions, chemical and noise pollution, habitat loss and tourism activities.

Information on abundance, density and population dynamics are fundamental for establishing management strategies for species conservation. The distribution and identification of areas in which biological and socially relevant behavior (eg. feeding, breeding, resting) are associated, are important information in the investigation of environmental issues and conservation.

Guiana dolphin (Sotalia guianensis) is a small coastal cetacean found along the south-western Atlantic Ocean, classified as Near Threatened in The IUCN Red List of Threatened Species and as Vulnerable in the Red Book of Endangered Brazilian Fauna. The species is in constant proximity to human activities being susceptible to a wide variety of threats. Many variables are influenced by environmental changes (eg. survival, reproduction, birth), and consequently influence the population trends and persistence over time. All these factors and variables act both, independently and combined, leading to different responses of the population.

Listed as an UNESCO World Heritage since 1999, the Cananéia Estuarine-Lagoon Complex, São Paulo state, Brazil, is located within the natural boundary between two state conservation units, Ilha do Cardoso State Park and Lagamar de Cananéia State Park and is included in the Federal Environmental Protection Area of ​​Cananéia-Iguape-Peruíbe and in the Wildlife Conservation Zone. Due to its great biological richness and well preserved status it is one of the most important coastal ecosystems in the country.

This study gathered historical, ecological and demographic information about Guiana dolphin throughout its distribution, estimated density, abundance and distribution within the estuary, and performed a population viability analysis for different scenarios of anthropogenic activities in the Cananéia estuary.

PVA is a way to predict the trends and probability of persistence or extinction of a species or population over time, incorporating demographic, ecological and environmental data of real populations in computer simulations of stochastic and deterministic models.

Although the Cananéia estuary is a well preserved environment and sustain a viable population of the species, the increase in anthropogenic activities in the estuary may lead to changes in population dynamics and habitat quality, compromising their persistence over time. 

This research was part of a PhD in Applied Ecology by the University of São Paulo, and counted on the support of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Instituto de Oceanografia (IOUSP) and Cetacean Society International (CSI).

Read article at Journal of the Marine Biological Association of the United Kingdom, by Cambridge University Press.

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