Translocation of Trapped Bolivian River Dolphins (Inia Boliviensis)
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J. CETACEAN RES. MANAGE. 21: 17–23, 2020 17 Translocation of trapped Bolivian river dolphins (Inia boliviensis) ENZO ALIAGA-ROSSEL1,3AND MARIANA ESCOBAR-WW2 Contact e-mail: [email protected] ABSTRACT The Bolivian river dolphin, locally known as the bufeo, is the only cetacean in land-locked Bolivia. Knowledge about its conservation status and vulnerability to anthropogenic actions is extremely deficient. We report on the rescue and translocation of 26 Bolivian river dolphins trapped in a shrinking segment of the Pailas River, Santa Cruz, Bolivia. Several institutions, authorities and volunteers collaborated to translocate the dolphins, which included calves, juveniles, and pregnant females. The dolphins were successfully released into the Río Grande. Each dolphin was accompanied by biologists who assured their welfare. No detectable injuries occurred and none of the dolphins died during this process. If habitat degradation continues, it is likely that events in which river dolphins become trapped in South America may happen more frequently in the future. KEYWORDS: BOLIVIAN RIVER DOLPHIN; HABITAT DEGRADATION; CONSERVATION; STRANDINGS; TRANSLOCATION; SOUTH AMERICA INTRODUCTION distinct species, geographically isolated from the boto or Small cetaceans are facing several threats from direct or Amazon River dolphin (I. geoffrensis) (Gravena et al., 2014; indirect human impacts (Reeves et al., 2000). The pressure Ruiz-Garcia et al., 2008). This species has been categorised on South American and Asian river dolphins is increasing; by the Red Book of Wildlife Vertebrates of Bolivia as evidently, different river systems have very different problems. Vulnerable (VU), highlighting the need to conserve and Habitat degradation, dam construction, modification of river protect them from existing threats (Aguirre et al., 2009). This channels, incidental mortality in fisheries, river pollution, VU categorisation is equivalent to that of the International boat traffic, and other threats jeopardise their survival Union for Conservation of Nature (IUCN) Red List. (Aliaga-Rossel, 2010; Choudhury et al., 2012; Kelkar et al., However, despite this, few actions have been proposed to 2010; Reeves et al., 2000). The negative effects of these improve the conservation status of this threatened species. threats, often combined, can occur in remote areas where The IUCN has recently listed Inia species as Endangered they are difficult to monitor. under the Red List assessment (da Silva et al., 2018), Uncontrolled agricultural frontier expansion, development increasing the importance of any conservation action to plans in rural areas, and overfishing are related to the protect the species. dramatic decline in river dolphin populations in the densely IUCN (2012), defined ‘conservation translocation’ as the populated regions of southern Asia. Habitat degradation deliberate movement of organisms from one site for release eventually led to the extinction of the Baiji (Lipotes in another, when the primary objective has a conservation vexillifer) in China (Reeves and Gales, 2006; Smith et al., benefit. These are high profile events that may bring the 2008; Turvey et al., 2007) and is threating the survival of opportunity to raise awareness of these river dolphin species the Ganges river dolphin (Platanista gangetica) in India and of the importance of protecting their habitat. This study (Wakid and Braulik, 2009). Irrawaddy dolphins (Orcaella describes the activities involved during the rescue and brevirostris) in the Mahakham River in Indonesia may be translocation of Bolivian river dolphins trapped in a segment facing the impacts of agricultural activities; with only 85 of a tributary river and also presents evidence of how individuals remaining from this once common species in the terrestrial habitat alterations affect river dolphin populations. heavily dammed Lower Mekong basin (Reeves et al., 2000). In South America there is little information on the effects of The Pailas River blockage habitat degradation on river dolphins, however, megaprojects In May 2010 (early dry season), authorities of the such as dams, roads and agricultural expansion are described Department of Santa Cruz, Bolivia, received information as threats for these species (Trujillo et al., 2010; Trujillo et about river dolphins trapped in the Pailas River, a small al., 2011). tributary of the Río Grande. According to the authorities, at The Bolivian river dolphin (Inia boliviensis), locally the end of April (end of high-water season) the unusually known as bufeo, is an endemic species of the upper Madeira strong current of the Río Grande rapidly changed its course, basin (Aliaga-Rossel, 2010) distributed in the Mamore, dragging sediment and sand, which accumulated against an Itenez and Abuna sub-basins in Bolivia. Molecular and embankment built to protect crops from possible floods. This morphometric studies indicate that the bufeo has the lowest caused an immediate blockage in the mouth of the tributary, genetic variability among all river dolphins and represents a isolating the Pailas River. The blockage consisted of a 3m 1 University of Hawaii, EECB Program, Hawaii, USA. 2 Museo de Historia Natural Noel Kempff Mercado (MHNNKM), Santa Cruz-Bolivia. 3 Current address: Research Associate, Institute of Ecology – Universidad Mayor de San Andrés, Campus Universitario n/n, 27 Street, Cota Cota, La Paz – Bolivia. 18 ALIAGA-ROSSEL & ESCOBAR-WW: TRANSLOCATION OF TRAPPED RIVER DOLPHINS Fig. 1. Location where river dolphins were trapped, figure based on aerial photographs. Pailas River, Rio Grande = Grande River, Santa Cruz- Bolivia. 1 = Pailas River areas with water levels from 20 to 50cm; 2 = water levels of ≤ 1 meter. 3 = Embankment. Black cross indicates Hermanos ranch. high pile of sand and sediments extending 500m from the water samples were taken following standard protocols and Río Grande into the Pailas River (Fig 1). The formation of submitted to the accredited Laboratory of Environmental the blockage was sufficiently quick to trap a group of river Quality of the University Mayor of San Andres in La Paz dolphins upstream of the blockage (F. Aguilera, pers. comm., (Table 1). 2011). The bufeos were trapped in a 3km long river segment; Following press coverage and public pressure, the but only about 1km within this segment was of suitable Ministry of Environment and the General Directorate of depth for the animals. The average river width and depth Biodiversity decided to respond to this event, contacting the were, respectively, 17m and 2.5m, but at either end the authors of this paper to investigate the situation and to find water depth was less than 0.7m, muddy and covered with a possible solution to release the trapped dolphins. An thick decomposing aquatic vegetation. As the dry season immediate inspection of the area was scheduled, and a plan progressed, the water depth diminished and by the end of the to relocate the animals was developed (Aliaga-Rossel and rescue the river was completely dry upstream of the Seis Escobar-WW, 2010). Hermanos cattle ranch (Fig. 1). Fishermen were interviewed during the first survey in METHODS the Pailas River to try to better understand how the river The trapped Bolivian bufeos were in a segment of the Pailas River (approximately at 16o18’S, 63o28’W) located 6 to 8 Table 1 hours drive from the city of Santa Cruz de la Sierra, Bolivia. Water quality analysis of the Pailas and Río Grande Rivers. Samples taken the first day of the translocation. The average annual temperature in this region is around 23°C and cold wind patterns called surazos can considerably lower Limit of the temperature during winter. The average annual rainfall Parameter Pailas River Río Grande River determination is 950mm and the hydrologic regime in the area is tightly Suspended solids 120–155 588–705 5 linked to precipitation and displays a unimodal curve, the Settleable solids <1.1 1.9 1 Total solids 750–1,031 1,360–1,430 10 months of greatest rainfall are January and February and the BOD-5 23–28 20–25 0.2 lowest water levels occur from May to early November Nitrates 1.7 0.22 0.3 (Guyot, 1993). Free cyanide <0.0096 <0.0096 0.0096 Total phosphorus 0.34 <0.070 0.07 Fecal coliform 90–230 230 2 Surveys and river evaluation Arsenic <0.0010 <0.001 0.001 To have the authorisation of the local authority, information Cadmium <0.020 <0.02 0.02 on water quality in the Pailas and Río Grande rivers was Mercury <0.0002 <0.0002 0.0002 Lead <0.05 <0.05 0.05 needed prior to the translocation of the bufeos. Therefore, J. CETACEAN RES. MANAGE. 21: 17–23, 2020 19 blockage and the trapping of the bufeos occurred. A list of searching for bufeo and then released the nets. The ends of mid-size fish, which included the bufeo’s prey (Aliaga- the nets were gradually moved towards each other, reducing Rossel and McGuire, 2010), was developed on the basis of the area available, to finally trap the dolphins. Once an opportunistic captures with a fishing net, or by recording the animal was trapped, it was immediately lifted to the surface, identity of dead fish found on the shores on the Pailas River. carefully maintaining its blowhole out of the water, and From May to August, ten surveys were conducted in the carried to be placed in a stretcher for transport. The bufeo river from an outboard motorboat to assess the distribution was then transported to a landing site built by the rescue team of the bufeos. Surveys followed strip transect methods. The called ‘Port B’ and located in the middle section of the Pailas boat travelled along the centre of the river at a constant River (Fig. 1). A small fenced off area made of plastic 1mm average speed of 7kmh–1 with observer eye height of 2m mesh and metal pipes was built in the river in case a newborn above water level (n = 10), with two observers plus a boat or young bufeo needed to be temporarily confined while the driver and additional people.