Interação dos golfinhos da Amazônia com a pesca no Médio Solimões

Abstract

For many years, Amazon dolphins remained protected by legends and superstitions. However, with the popularization of nets and the exploitation of new fishery resources, the conflicts are constantly increasing. The dolphins in the medium Solimões river (Tefé, AM and surroundings) are threatened mainly by two antropic sources: accidental mortality in fishery and the use, especially of boto, as bait to piracatinga´s fishery. Although we have no evidences that Amazon dolphins are threatened in all its distribution, antropic impacts can threaten local populations. The populations of botos and tucuxis in the medium Solimões river are facing reductions, probably due to the impacts caused by fisheries activities. Despite the difficulty on establishing safe levels to populations decline, the mortality limit (ML) applied in this study can be a usefull tool in the handling of dolphin s populations. The objective of this study was to describe the interactions between these dolphins and fisheries in the region and the possible implication for its conservation. During 11 months, from February to December of 2010, 180 fishermen and 17 piracatinga`s fishermen were interviewed using mixed questionnaries, 432 fisheries operations were followed, one Fishing Association and seven cold storages were surveyed in the cities of Tefé, Alvarães, Uarini and its near communities. Tramalha (gillnets) is the gear most used and there is supremacy in the use of nets. According to fishermen, interactions with botos, alligators, giant otters and tucuxis are frequent, with boto being the most common. 90,28% of the fisheries activities monitored had operational interaction with some species other than targeted ones. Interactions with dolphins occurred in 78,47% of the activities and were observed a difference between the two species: interactions with botos are more common. To the boto the most frequent interaction was tocaia (ambush), and the gear most involved were gillnets. Prevalence of negative interactions afffecting the fishermen were also observed. Flooded and Dry seasons were significant in the occurrence of operational interactions and also had prevalence of interactions in calm water locations. We registered 24 dolphins involved in negative interactions for them, being 21 botos and three tucuxis. We estimated 176 botos and 26 tucuxis as the total number of dolphins killed in negative interactions. The dolphins are not consumed nor used on mystical activities in the region and the inclusion of boto as bait for piracatinga´s fisheries was the only reported use. Piracatinga´s fishers did not identificated this fish as main targeted species but as an alternative of fast money return. The procedure for this fishery includes the device known as box . The bait used can be meat of alligators, botos or catfish´s guts, with preference for boto. Stories about fishermen already specialized in the boto´s or alligator´s capture for bait supply are common. The annual piracatinga´s production of cold storages in the region is around 420 tons. The productivity of piracatinga´s fishery is about 250 kg per fisherman per hour. The use of tucuxi for this activity was not evidenced. To boto, we got a rate on 1 kg of bait to attain 3,2 kg of piracatinga and estimated that 170 botos die per year due to this activity in the region. The estimatives of mortality had been defined in 346 botos and 26 tucuxis per year as a result of fisheries interactions and we established 48 botos and 43 tucuxis as the sustainable death rate for each animal. We conclude that, both on fishermen´s mind and in true operational interactions, the Amazon dolphins interact in different ways with fishery. The operational interactions with dolphins are extremely frequent in the studied region and its prevalence generates the conflicts observed between fishers and botos, therefore, this must be the reason to the current reduction of boto´s population in the studied area. The boto is seriously threatened and conservation´s interventions need to be swift and decisive.