DISTRIBUIÇÃO E ESTIMATIVAS POPULACIONAIS DO BOTO Inia geoffrensis (DE BLAINVILLE, 1817) (INIIDAE) NO MÉDIO RIO ARAGUAIA (BRASIL CENTRAL)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

This is the first study about the abundance and density of the boto Inia geoffrensis using Distance sampling in the Araguaia River (Central Brazil). The study was carried out along a 530 km section of the Middle Araguaia River. The surveys were conducted in May and September 2009 (during falling and dry water seasons), where strip and line transects were employed. Almost all observations were of single animals (88.3% - May and 74.3% - September). The mean group size was 1.23 (SD = 0.49; n = 195). The boto density from DISTANCE was 0.84 botos/km2 and the abundance was 83; from the strip transect the mean density was 0.75 botos/km2. The results allowed us to infer that the abundance of botos of the section of the middle Araguaia River is about 1/4 of the entire river length. However, it is known that dolphins are not uniformly distributed along the river and the extrapolation of estimates obtained in this study for the entire length of the Araguaia River should be made with caution. This study aimed to characterize the distribution of boto along of the middle section of the Araguaia River (Central Brazil) and verify the existence of preferred habitats of this species. Data collection occurred in May (falling water season) and September (dry water season) 2009. We collected data about the occurrence of the group and habitat type. The habitats were quantified and georeferenced and the river was divided into nine segments according to their geomorphological features (and later grouped into SEG I and SEG II, low and high amount of sediment, respectively). Throughout the area studied, a total of six types of marginal habitats were identified (Bank with Vegetation, Bank, Beach, Mouth, Remanso and Island). The river was divided into segments according to the geomorphology of the course. There were a total of 195 sightings (239 botos). The botos did not occur uniformly in all habitats, with higher densities in certain types of habitat. The habitat with the highest density of botos was the Mouth of rivers followed by the habitat Remanso. The group sizes also varied according to the habitat. The distribution of these animals was not uniform along the area covered in the study, showing highest density in SEG II than in SEG I. The distribution and habitat of these dolphins are closely related to the distribution of their prey and the seasonal change of the river and consequent marginal habitat types along the river.

ASSUNTO(S)

boto (mamífero aquático) araguaia, rio inia geoffrensis zoologia

ACESSO AO ARTIGO

Documentos Relacionados