Resumen

ALIAGA-ROSSEL, Enzo et al. Distribution and population status of the Bolivian river dolphin (Inia boliviensis) in four tributary rivers of the Mamore River sub basin. Ecología en Bolivia [online]. 2012, vol.47, n.2, pp.134-142. ISSN 1605-2528.

The Bolivian river dolphin or bufeo (Inia boliviensis) is the only cetacean in Bolivia and despite its endemic status basic knowledge about it is still scarce. Both the action plan for South American river dolphins and the Red Book of Vertebrates of Bolivia highlighted the need for further studies on distribution and abundance. This study responds to these demands during the season of rising waters in four tributaries of the Mamore, the Ibare, Niquisi, Tijamuchi, Apere and two lagoons. We used the standardized modified transect band method travelling on a boat at a constant speed of 7-9 km/h. Transects were conducted between 7:00 and 17:00, sightings of river dolphins and other habitat characteristics were recorded. From 45-50 h of sampling were employed in the surveys and a total of 199 sightings were obtained. The largest proportions of sightings were solitary individuals (59.14%), followed by pairs and a single group of eight individuals in the river Apere. The physic-chemical characteristics of the river did not seem to influence the river dolphins distribution. This study provides information on the populations of river dolphins in support of national and regional initiatives to preserve the species. Even though the encounter rates reported in this study are amongst the highest in South America, comparisons with previous studies in the same tributaries suggest a population decline.

Palabras clave : Distribution and abundance; Iniageoffrensis boliviensis; river dolphin; Upper Madeira basin.

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