Abstract
Brycon nattereri is a threatened fish species restricted to small headwater rivers of the Parana, Sao Francisco and Tocantins rivers. This species has been extirpated from many sites, and little is known about its ecology. In this sense, the present study investigated temporal variations in the occurrence, abundance and length structure of B. nattereri in the Dois Irmaos river, a small headwater river from the Tocantins river basin. Samples were taken monthly between January and November of 2009 and 2010. The studied site comprised a 4.5 km river stretch, sampled with an active fishing method (fly fishing). Individuals caught were counted, measured and returned immediately to the river. We caught 302 individuals along two years. Brycon nattereri was present in the studied stretch in all sampling months, with higher abundance between November and May (wet season). We registered a wide range of lengths, with predominance of adult fish; young were captured in July and August, indicating recruitment in the region. The present study, therefore, showed that populations of B. nattereri, an endangered fish species, still persist in small headwater rivers of the upperTocantins river.
Highlights
The genus Brycon includes 42 valid species (ESCHMEYER; FONG, 2014), distributed across different river systems of South America
The present study investigated the existence of relict populations of B. nattereri in the upper Tocantins river basin
Brycon nattereri was present in the river stretch during all sampling months (Figure 2), except in October 2010, when the stretch was disturbed by fire and sampling was not performed
Summary
The genus Brycon includes 42 valid species (ESCHMEYER; FONG, 2014), distributed across different river systems of South America. Most species are rheophilic and migratory, but some have specific habitat affinities, such as the pirapitinga Brycon nattereri Gunter, 1864. This is a medium-sized fish (maximum standard length = 27.9 cm) found in headwaters of the Paraná, São Francisco and Tocantins river basins, restricted to lotic environments with the presence of riparian vegetation (LIMA et al, 2008). It has been extirpated from many headwater systems (LIMA et al, 2008; ROSA; LIMA, 2008); as a consequence, B. nattereri is currently listed as ‘threatened with extinction’ in the Brazilian official list of threatened species (ROSA; LIMA, 2008)
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