Sazonalidade no uso de habitats pelo peixo-boi marinho (Trichechus manatus LINNAEUS, 1758) na Praia de Picos, Icapui - CE

Abstract

The manatee, Trichechus manatus (Linnaeus, 1758), is an aquatic mammal that belongs to the family Trichechidae (Order Sirenia). The species is herbivore and occurs in shallow waters where plenty vegetation and fresh water sources are available. The species is classified as Vulnerable by IUCN (2012). Even though marine mammals usually exhibit high mobility and dispersion capacity as if there would be no geographical barriers in the ocean, some species such as the manatee have restricted distribution, reflecting ecological requirements and their centers of geographical origin. It occurs in the east coast of Ceará State between the towns of Beberibe and Icapuí. Moreover, the latter considered an important area of manatee occurrence, as it combines ecological attributes essential to the maintenance of the species in the region. The aim of this study was to determinate the frequency of use of the Picos Beach, Icapuí (04°39'24"S / 37°26'59"W; 04°39'37"S / 37°25'58"W), by individuals of manatee, describing spatial and temporal use patterns. In order to record the distribution of the animals, an area of 1 km2 was selected and divided into four quartiles of equal size (Zones 1, 2, 3 and 4). The monitoring was carried out from a fixed point installed on top of a cliff on Picos Beach between February and December 2012, three times a week, with a daily effort of six hours (7-10h; 13-16h). The observations were made by naked eye and with the aid of binoculars. The recordings were made by sighting continuous ad libitum, observing all the animals that appeared during each monitoring period (morning and afternoon). The time of residence represented 43.5% of the total sighting effort. The individuals of manatee occurred during all the year in Picos Beach with a frequency varying between 80 to 100% among the monitored months. The mean residence time of individuals was 48.1 minutes (± 50.9 minutes), suggesting that the Picos Beach is an important area for the species, which may use it as a foraging, feeding, reproduction and rest habitat. There was seasonal preference for the Zones 1 and 3, which have higher depth and tide level, and a greater proportion of muddy substrate and grass stands, in comparison to the other zones. This study revealed information about the manatee´s habitat use at Picos Beach, which is relevant to direct further research on the use of resources and ecology of this species. Futhermore, it could help develop conservation and management strategies in the region, mainly due to the confinement of populations of this species in northeastern of Brazil.