Biology Reference
In-Depth Information
indicates how mining contaminant bi-products might be affecting the bufeo population,
constituting a serious threat for the species located at the top of the food chain.
Hunting and Fishing
There is no strong evidence in Bolivia that people living in the area kill bufeos as a
source of protein in their diet. However, in Brazil, Colombia, and Peru a main human cause of
mortality comes from the death of individuals trapped in fishing nets. Although some of these
trapped bufeos are released, in many cases the fishermen let them die or kill them with
machetes to avoid damages to their catch and nets. In such cases it is common for the
fishermen to use the remains as bait
(Best & Da Silva, 1989; Reeves et al., 1999; Aliaga-
Rossel, 2002). However, interviews with fishermen in the central and downriver portions of
the Mamore River indicate that the fishermen do not consider the bufeo to be a competitor for
their fish (Aliaga- Rossel, 2002), as is the case in the Pacaya-Samiria National Reserve in
Peru. Here, commercial fishing is a problem, and there have been reports that the dolphins
have been intentionally poisoned using methyl-parathion (Reeves
et al.,
1999). Also a report
from near of Tefé, in the Brazilian Amazon, indicates the intentional kills to use as bait,
where 1650 bufeos were estimated to be killed per year (V. da Silva 2008 com.pers).
There are only a few studies that have focused on the effects of commercial fishing and
the possible impact on aquatic populations. Commercial fisheries in Bolivia are not as
extensive compared to neighboring counties. There are reports that some members of the
indigenous group, the Yucararés, occasionally hunt bufeos to sell the fat in towns around the
area of Trinity City. This seems to be an income-generating practice. Bufeos are also shot for
amusement or by sport hunters practicing their aim (R. Cuellar 2008 com. Pers; Aliaga-
Rossel 2003).
Navigation
The increase in boat traffic on the rivers has had a negative effect on the bufeos and other
aquatic fauna (Constantine et al., 2004; King & Heinen, 2004; Lusseau 2003). A similar
observation was made in the study of Pilleri & Gihr (1977), indicating that the increase in
boat traffic and the construction of new roads are harmful for the species, were the
construction of new roads lead to river bank erosion problems. The increase in traffic is a real
threat for the bufeos causing acoustic contamination which can affect communication,
orientation and stress for the bufeos, but also the effects of the leakage of oil from boats.
Bufeos can also be injured or killed by boat propellers. A necropsy was performed on a
bufeo from the Tijamuchi River (Aliaga-Rossel, 2000) and it was found that the animal had
probably been struck by an outboard motor propeller. The left side of its beak was heavily cut
and the lower left jaw was broken. Although this was an isolated registered event, deaths by
boats have been documented in the Colombian Amazon (Trujillo, 1992). This danger
increases during the low water season when more neonates are observed (McGuire and
Aliaga-Rossel, 2007) and dolphins use shallow river channels that are also used by fishing
boats and other vessels. In some areas (i.e. the Yacuma River), an increase in unorganized
tourism and the offer of swimming with dolphins increases boat traffic and results in
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