Distribución y estado poblacional del bufeo boliviano (Inia boliviensis) en cuatro ríos tributarios de la subcuenca del Río Mamoré
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Ecología en Bolivia
Abstract
El delfín de río boliviano, también llamado bufeo (Inia boliviensis), es el único cetáceo en Bolivia y el conocimiento sobre su ecología básica aún es escaso. Tanto el Plan de Acción para los delfines de río de Sudamérica como el Libro Rojo de Vertebrados de Bolivia resaltan la necesidad de continuar con estudios de distribución y abundancia. Este estudio cubre estas demandas durante la estación de crecida de aguas, en cuatro ríos tributarios del Mamoré: Ibare, Niquisi, Tijamuchi y Apere, además de dos lagunas. Se recorrieron estos ríos utilizando el método estandarizado modificado de transecto en banda. Los transectos fueron realizados en un bote que viajaba a una velocidad constante de 7-9 km/h entre las 7:00-17:00, desde el cual se registraron avistamientos de bufeos, además de otras características del hábitat. Con 45-50 horas de muestreo, se registraron 199 avistamientos de bufeos. En total, la mayor proporción de avistamientos fue de individuos solitarios (59.14%), seguido de pares y un solo grupo de ocho individuos en el Río Apere. Las características fisicoquímicas parecen no influir en la distribución de los bufeos .Este estudio brinda información poblacional de los delfines de río en apoyo a las iniciativas nacionales y regionales para su conservación. Si bien las tasas de encuentro registradas en este estudio están entre las más altas en Sudamérica, la comparación con estudios previos en los mismos ríos sugiere una reducción en las poblaciones de bufeos.
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.
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.
Description
Vol. 47, No. 2