Encounter rates of the Bolivian river dolphin (Inia boliviensis) in northeastern Bolivia (original) (raw)
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Endangered Species Research, 2020
The Bolivian river dolphin, known locally as the bufeo, is one of 4 species of river dolphin in South America. Endemic to the upper basin of the Madeira in the Bolivian Amazon region, the species is categorized as Endangered on the IUCN Red List. This article provides information related to the geographic distribution of the species, and a review of the studies of its abundance that have been conducted in Bolivia since the 1970s. We discuss the surveys, the analysis methods used in the different studies, and the ways in which these methods might influence the population estimates. We found 63 population abundance estimates for the Bolivian river dolphin across 17 reviewed publications. These studies report relative abundance data for rivers that range from 0.2 to 2.81 bufeos km−1, and density ranges from 0 to 7.59 bufeos km−2. The information presented here reflects the knowledge of the population size of the species in Bolivia obtained over 4 decades, and will be useful for developing conservation strategies and as a tool for decision makers.
Aguas del Iténez o Guaporé Recursos hidrobiológicos de un patrimonio binacional (Bolivia y Brasil), 2013
The Bolivian river dolphin (Inia boliviensis) was recently recognized as a species, geographically separated from Inia geojfrensis by rapids in the Madera River. The species is restricted to the Iténez*, Yata and Mamoré watersheds. More or less 95% of its distribution range overlaps with Bolivian territory, the remaining part with Brazil. Overall, the species is poorly studied, with an important information gap on its distribution and abundance in the Iténez river basin. As a first step towards the development of conservation strategies in this basin, habitat preferences and current population status are being assessed. The aim of the present study was to determine the population status of the river dolphin in the San Martin and Blanco rivers, two tributaries of the Iténez River. During the end of the high water season, 81.6 km were surveyed in the San Martin River and 66 km in the Blanco River. The average size of the observed groups was 2.4 (+2.1) in the San Martin River and 3.0 (± 2.0) in the Blanco River. The relative abundances were 0.7 and 1.4 individuals/km respectively. In the San Martín River, there was a significant preference for river confluences. Hypotheses are put forward to explain observed differences in relative abundance between the two rivers.
Conservation of the River dolphin (Inia boliviensis) in Bolivia
-Garcia, M & J. Shostell (Eds.) 2010. Biology, Evolution and Conservation of the River dolphins in South America and Asia: Unknown dolphins in danger. , 2010
The pink river dolphin genus Inia, is widely distributed in the Orinoco and Amazon basins. Locally called the bufeo (Inia boliviensis) in Bolivia, it is an endemic species to the region, geographically isolated from Inia populations within the Amazon's main stem by a series of rapids between Guayaramerin, Bolivia and Porto Velho, Brazil. In Bolivia, they are distributed in three main sub-basins: Abuna, Mamore and Itenes (Guapore). Despite bufeo being a native species and the only cetacean present in a land-locked country, its ecology and conservation status are poorly understood. Unfortunately, no conservation laws explicitly target this cetacean in Bolivia and consequently it only receives relatively minor legal protection when it resides in protected conservation areas. This chapter includes information on the studies that have been conducted in Bolivia; the conservation status; aspects related to the geographic distribution of the species, its behavior, ecology, population size, threats and possible means of protection. This information will lead to recommendations for the implementation of priorities in research programs and conservation for this species in Bolivia.
Biotropica, 1998
The distribution, habitat association, group size, population structure, and prey availability of river dolphins (/nia geojJrensis) were studied from November 1993-June 1994 in the Cinaruco River, a tributary of the Orinoco River that forms the southern boundary of Venezuela's Santos Luzardo National Park. Dolphins were sampled from a boat using modified strip-width transects, for a total of 418 h. The study area was 1.67 krn2, and contained 20 krn of water courses. Like other rivers of this region, the Cinaruco River undergoes a seasonal flood cycle. Dolphins were seen most often during the period of falling water (41 % of total sightings) and least ofren during the rising water period (24% of total sightings). Dolphins were seen most ofren in confluence areas (35% of total sightings) and were seldom seen in side channels (13% of total sightings). The presence of rocks or sandbanks was associated with a greater frequency of dolphin sightings, and sightings increased with habitat heterogeneity. Average group size for the 8-mo study was 2.0 (:t 1.0) and was largest during the rising water period. Calves were first sighted during the end of the dry season and became more common during the early flood season. Six individuals were photo-identified and resighted with one sighted eight times over 186 d. The fish diversity of the study area was high, with 161 species documented in our samples. The stomach of one /nia contained 15 fishes representing at least 4 species. RESUMEN Se estudi6 la disttibuci6n, asociaci6n con el habitat, tamafio de los gtupos, estructuta poblacional y disponibilidad de presa del delfin de rio (lnia geoffiensis) desde noviembre 1993-junio 1994 en el rio Cinaruco, un tributario del rio Orinoco que forma ellimite sur del parque nacional venewlano Santos Luzardo. Se tomaron muestras de los delfines desde un bote usando el metoda modificado de la transecta en banda, durante 418 h de esfuerzo. El area de estudio comprende 1.67 krn2 y contiene 20 krn de cursos de agua. AI igual que otros rios de esa regi6n, el rio Cinaruco sufre inudaciones ciclas. Los delfines fueron avistados mas frecuentemente durante el periodo de la bajada del agua (41% del total de los avistamientos) y menos frecuentemente durante el periodo de crecida del agua (24% del total de los avistamientos). Se vieron mas delfines en las areas de con/luencia (35% del total de los avistamientos) y raramente en los canales laterales (13% del total de los avistamientos). La presencia de cocas 0 bancos de arena estuvo asociada con una mayor frecuencia de avistamiento de delfines, y los avistamientos aumentaron con la heterogeneidad del ambience. El tamafio promedio dellos grupos durante los 8 meses de estudio rue 2.0 (:t 1.0) Y rue mayor durante la crecida de las aguas. Las crias se avistaron primero al final de la estaci6n seca y se hicieron mas comunes al inicio de la epoca de crecida de las aguas. Seis individuos se identificaron con fotograffas y se avistaron nuevamente, uno de los cuales rue avistado ocho veces a 10 largo de 186 d. La diversidad de peces en el area de estudio era alta, documentandose 161 especies en nuestras muestras. El contenido estomacal de un lnia estaba compuesto For 15 Feces, representando For 10 menos 4 especies.
Marine Mammal Science, 2012
This study is part of an ongoing effort to evaluate and monitor river dolphin populations in South America. It comprises the largest initiative to estimate population size and densities of Inia and Sotalia dolphins using statistically robust and standardized methods. From May 2006 to August 2007, seven visual surveys were conducted in selected large rivers of Bolivia, Colombia, Brazil, Ecuador, Peru, and Venezuela in the Amazon and Orinoco river basins. Population sizes of Inia and Sotalia were estimated for different habitats (main river, tributary, lake, island, confluence, and channel). A total of 291 line and 890 strip transects were conducted, covering a distance of 2,704 linear kilometers. We observed 778 Inia geoffrensis, 1,323 Inia boliviensis, and 764 Sotalia fluviatilis. High-density areas were identified (within 200 m from the river banks, confluences, and lakes) and we propose that these constitute critical habitat for river dolphins. High densities of river dolphins seem to coincide with well-managed freshwater protected areas and should be considered as hot spots for river dolphins in South America.
Latin American Journal of Aquatic Mammals
To estimate river dolphin habitat preference through density, as well as which habitats were preferred for feeding in the Pacaya- Samiria National Reserve, surveys were conducted during the high- to low-water season transition, from 2016 to 2018, in the channels, lakes, and confluences of the Samiria River. Both the Amazon river dolphin and tucuxi dolphin showed a preference for the confluences. The wide channel (Amazon: 24.8 dolphins/ km2, tucuxi: 7.6 dolphins/km2) and narrow channel (Amazon: 73.0 dolphins/km2; tucuxi: 6.0 dolphins/km2) also had high dolphin densities, especially for the Amazon river dolphins. In contrast with previous studies, the lakes had the lowest densities of dolphins for both species. High proportions of feeding behavior were observed in the confluence and wide channel habitats. The potentially larger presence of fish in these two habitats is likely the primary reason for the high dolphin densities. The high dolphin densities in the narrow channel, on the ot...
Endangered Species Research, 2021
Studying the variables that describe the spatial ecology of threatened species allows us to identify and prioritize areas that are critical for species conservation. To estimate the home range and core area of the Endangered (EN) Amazon river dolphin Inia geoffrensis, 23 individuals (6♀, 17♂) were tagged during the rising water period in the Amazon and Orinoco river basins between 2017 and 2018. The satellite tracking period ranged from 24 to 336 d (mean ± SE = 107 ± 15.7 d), and river dolphin movements ranged from 7.5 to 298 km (58 ± 13.4 km). Kernel density estimates were used to determine minimum home ranges at 95% (K95 = 6.2 to 233.9 km2; mean = 59 ± 13.5 km2) and core areas at 50% (K50 = 0.6 to 54.9 km2; mean = 9 ± 2.6 km2). Protected areas accounted for 45% of the K50 estimated core area. We observed dolphin individuals crossing country borders between Colombia and Peru in the Amazon basin, and between Colombia and Venezuela in the Orinoco basin. Satellite tracking...
Latin American Journal of Aquatic Research, 2017
We present results of the first simultaneous visual and acoustic surveys for Amazon River dolphins (Inia geoffrensis) and tucuxi (Sotalia fluviatilis), undertaken in Yarinacocha Lagoon, Ucayali, Peru (length = 20 km, area = 12 km 2). A total of 324 Sotalia observations and 44 Inia observations were recorded in boat-based transects. Based upon total survey effort, we estimated Sotalia had a mean density ± SE of 1.98 ± 4.6 ind km-2 and an overall abundance of 34 individuals (95% CI: 28 to 40). Average density for Inia was 0.2 ± 1.2 ind km-2 with overall abundance estimated at 3 individuals (95% CI: 0 to 8). Visual surveys observed more Sotalia individuals during earlier hours of the day and during the dry season. Preliminary acoustic surveys undertaken with C-POD passive acoustic monitoring devices indicated a diel pattern in detections of cetacean vocalization with more diurnal activity and with detections ceasing from midnight until 10:00 AM. This work highlights the possibility of monitoring both river dolphin species through visual and acoustic surveys to generate baseline information on abundance trends and distribution patterns in the Ucayali region, an area with high levels of human disturbance.
Marine Biodiversity Records, 2012
gabriel m.a. dos santos 1,2,3 , adriano c. quaresma 3 , rafael r. barata 3 , bruna m.l. martins 1 , salvatore siciliano 1,4 , jose ' de sousa e silva jr 1 and renata emin-lima 1,5