The Franciscana ( Pontoporia blainvillei ) in the Northern Limit of the FMA II : Strandings and Habitat Use in I lha G rande B ay

Abstract

The presence of the franciscana ( Pontoporia blainvillei ) at the northern limit of the FMA II was investigated using a range of methods, including monitoring of strandings, boat surveys, and passive acoustic monitoring (PAM). Franciscana strandings were recorded within the distributional gap between Macaé (22°55′ S) and Ilha Grande (23°09′ S), suggesting that the northern boundary of the FMA II may extend as far as Jaconé (22°56′ S; 42°38′ W). Furthermore, habitat use in Ilha Grande Bay was investigated through a combination of boat surveys and PAM efforts. Our findings support the idea that the species use Ilha Grande Bay year‐round, both day and night, and this bay might be the primary habitat of P. blainvillei in the FMA II section of the Rio de Janeiro coast. In Ilha Grande Bay, the franciscana is widely distributed over an area of more than 300 km 2 , along isobaths between 8 and 30 m. There were multiple detection events at the same PAM station during the day, indicating that the species was present at different times of day at the same location. Average group size was 7.7 (±6.7). While P. blainvillei occupies a large area of the bay, further investigation is needed into its use of shallower waters and the deeper, central portion of the bay, as well as the presence of areas with higher individual densities.

Bibliographic Information