Abstract

ESPINOZA-RODRIGUEZ, NÍNIVE et al. Seabirds and Sotalia guianensis associations at the southern Gulf of Venezuela. Caldasia [online]. 2015, vol.37, n.2, pp.309-318. ISSN 0366-5232.  https://doi.org/10.15446/caldasia.v37n2.54381.

Associations between seabirds and marine mammals are a common event in all seas and oceans of the world. Several authors have called these associations as commensal, opportunistic or parasitic relationships, depending on the result of such interaction effect on one or two related species. In order to describe the presence of associations among Sotalia guianensis and sea birds in the southern region of the Gulf of Venezuela, from June 2011 to June 2012, observations of groups of this cetacean and seabirds were made on mobile platforms, using the "group follow" protocol following an "Ad libitum sampling". All sightings were geo-referenced and annotations about the occurrence or non-association with seabirds, species and number of birds present at the association were made. During the sampling period 721 sightings were recorded, of which 197 events of aggregation between seabirds and S. guianensis were registered. The resident seabird species most frequently presented at each event associated with S. guianensis were: Fregata magnificens (49%; n=98), Phalacrocorax brasilianus (29.5%; n=59) and Pelecanus occidentalis (22.5%; n=45); being Thalasseus maxima (71%; n=142) the only migratory species. During all sampling sightings was observed only one interaction between a swallow species (Riparia riparia) and Sotalia guianensis. These bird-dolphin associations were only observed when a notable congregation of fish was registered and a dolphin or a group of dolphins were performing any activity with large movements of water that allowed birds to find and locate their preys with low energy cost.

Keywords : Seabirds; Sotalia guianensis; Navigation channel; Gulf of Venezuela.

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