Conflicts with fisheries and intentional killing of freshwater dolphins (Cetacea: Odontoceti) in the Western Brazilian Amazon

Abstract

We report three cases of conflicts with fishing activities of freshwater dolphins Inia geoffrensis and Sotalia fluviatilis in the Western Brazilian Amazon. The animals presented several cuts produced by perforating and cutting objects, especially on the dorsum, sides and flukes. The wounds were probably caused by harpoons and machetes, gear commonly used by local inhabitants for fishing and agricultural practices in the Amazon. The carcasses had not been subsequently used in any way, which suggests that the animals were not killed for consumption. Conflicts with fishermen and persistent cultural taboos may have led to the deaths. These records are an indication of a growing situation of conflict with fishing activities that should be taken into consideration in the conservation policy planning of aquatic mammals in the Amazon.

Conflicts between river dolphins (Cetacea: Odontoceti) and fisheries in the Central Amazon: a path toward tragedy?

“…Depredation, i.e., the removal or damage of fish caught in fishing gear, causing a reduction in market value, was identified by READ (2008) as a source of conflict with fishermen, a finding corroborated by our results. In addition, fishermen may take retaliatory attitudes towards the animals due to real or perceived monetary losses (LOCH et al 2009), which was also corroborated in the present study.…”

“…In the present study, interviewees described mortality as related to the fact that the animals cause damage to fishing gear. Corroborating this, LOCH et al (2009) stated that these dolphin species are captured in order to prevent their acquisition of commercially valuable fish species and/or the damage of fishing gear, indicating that there is competition between the local fishermen and these dolphins for fishery resources.…”

“…MANGEL et al (2010) reported that harpooning dolphins for bait is common among the artisanal fisheries conducted on the Peruvian coast, but that all cetaceans harpooned after entanglement, both by gillnet and longline vessels, were used as bait, showing that, in that case, fishermen killed the dolphins with the intention of using their meat as bait. Accordingly to LOCH et al (2009), reports of negative attitudes towards cetaceans with no apparent motive are common in the region of their study, the western Brazilian Amazon, especially towards the boto, considered by the local inhabitants as bad-tempered and capable of disrupting fishing activities.…”

“…Confirmed hostility towards dolphins on the part of the commercial fishermen has been documented (DA SILVA & BEST 1996, LOCH et al 2009). This hostility, which could have negative impacts on both dolphin species, has been traditionally countered by numerous protective superstitions about the dolphins (DA SILVA 1990).…”

“…According to LOCH et al (2009) the conflicts between these animals and the fisheries can be ecological, when there is predation of commercially important fish stocks, or operational, resulting in physical encounters with fishing gear. The increased pressures from the fisheries in the Central Amazon in recent decades has greatly heightened the potential for river dolphin/fishery interactions; this in turn could adversely affect the status of the dolphins, through higher rates of incidental mortality in fishing gear, through direct competition for certain fish species (DA SILVA & BEST 1996), and more recently through the use of boto carcasses as bait during fishery activities (DA SILVA et al 2011).…”