The environmental organization WWF, through its Living Amazon Initiative and WWF Brazil has begun a study of the migratory fish species known locally as matrinxã (matrinsham) in the region of the Salto Augusto Falls inside the Juruena National Park, a protected area that encompasses areas of the Brazilian states of Amazonas and Mato Grosso.
The matrinxã (Brycon amazonicus) is a fish renowned for its silvery brilliance and delicious flesh. Adults can be up to 70 cm long and weigh 4 kilos and they are much appreciated by sport anglers. More importantly, they are an source of protein in the diet of local communities.
The study being undertaken by WWF is concentrated in the region in the waters immediately above and below the beautiful Salto Augusto falls, located inside the National Park’s limits. There researchers captured ten specimens of matrinxã above the falls and ten below and they will be unmaking genetic tests to discover whether the communities of matrinxãs above and below the falls are exactly the same species or not.
The 20 specimens are now at the laboratories of the Federal University of Mato Grosso in the city of Cuiabá and they will be studied by a team led by fish zoology specialist Paulo Cesar Venere. The study is expected to be finalised in July.
In addition, the field researchers have collected samples of the fins of 15 other specimens to provide more information to support the genetic testing of the matrinxãs.
The Migratory Species of the Juruena River Expedition to the surrounding regions of the Juruena National Park, which lies in the Tapajos River basin, began on May 12 and is scheduled to finish on May 24, World Fish Migration Day.
Differences are important
According to one of the biologists involved in data gathering in the field, Reginaldo Carvalho dos Santos, it is very important to find out whether there are any differences between the matrinxã population above the Salto Augusto falls and that below them.
“If we can prove that the two communities are different, then it means we have two distinct environments, so the waters above and below the falls must have different characteristics in regard to oxygen levels, conductivity rate, and temperatures too”, he declared.
Reginaldo stated that if what the fishermen are saying is true then the conservation activities directed at the two environments also need to be differentiated and take into consideration their respective characteristics. “If we want to conserve the matrinxãs and even the falls themselves, then we must adopt distinct approaches and address the two environments differently”, he explained.
According to Living Amazon Initiative leader Claudio Maretti, this initial study is designed to acquire a better understanding of migratory fish species dynamics and the social and economic aspects of the communities in regard to available resources. “The government has identified the Tapajos River basin as the next ‘frontier’ for hydroelectric dam construction in the Amazon. The construction of a hydroelectric dam completely alters the ecological, social and economic dynamics of a region and so it is of fundamental importance to get to know those aspects beforehand”, he explains.
“We can envisage the construction of dams as having similar impacts on the rivers as deforestation has on the forests because both of them convert natural ecosystems into highly altered zones. However great national interest in producing clean energy may be, local and indigenous communities have every right to be heard in regard to the dams’ impacts on their areas and societies and they must discuss the benefits and impacts that can be expected”, adds Maretti.
Juruena River Expedition
This study of the matrinxã species is part of a series of much broader initiatives designed to acquire more in-depth knowledge of the Juruena River’s fishery resources. The survey of fishing activities made use of a questionnaire to interview riverside families along the Juruena River and in local communities like Barra de São Manoel and Pedro Colares, in the municipality of Apuí, in the state of Amazonas.
This survey instrument will enable WWF to identify the types of fish that are most sought after by fishermen in the region; how often fishing is carried out; in which stretches of the river the fish are caught and who are the people involved in fishing activities.
The study also embraces guest houses and tourist guides operating in the area so that a comprehensive portrait of all fishing activities in the region, including sport angling, can be obtained.
Some of the work is still in course but on May 24 the researchers will go back to their bases to compile data and analyse the results for dissemination.
In order to carry out this work, WWF was able to count on the collaboration of the Chico Mendes Institute for Biodiversity Conservation (ICMBio), the governmental body that issued the fishing permissions for the survey. For part of the time, a member of the National Park management staff accompanied the Expedition.