Abstract
ABSTRACT Mylesinus paucisquamatus is a threatened fish endemic to the rio Tocantins basin, with little information about its natural history. Using monitoring data obtained between 1998 and 2009, we investigated the spatial distribution, feeding and reproduction of this species in a long stretch of the middle-upper rio Tocantins. Eighty-one individuals were captured over a decade of intensive sampling. In addition, we recorded the species in only 13 out of 35 sites, particularly in the Tocantins and Paranã rivers. Most individuals were captured alone, while the remaining formed small groups. These results indicate that this fish is rheophilic and rare. We recorded seasonal variation in fish abundance, with higher values during the dry season, indicating seasonal movements. The species is herbivorous and specialized in the consumption of plants attached to substrates, particularly bryophytes. We also observed seasonality in reproduction, since reproductive activity increased during the early dry season. These ecological traits, e.g. , rarity, rheophilic and specialized feeding habits, indicates that M. paucisquamatus is vulnerable to environmental changes, particularly river damming. Considering that three large dams currently regulate and fragment this section of the rio Tocantins, the persistence of this species is jeopardized, demanding effective conservation actions.
Highlights
Mylesinus includes three valid species (Eschmeyer et al, 2015), distributed in river systems of the Amazon basin and central Brazil
Mylesinus paucisquamatus has been recorded in streams of the upper rio Tocantins basin (Miranda & Mazzoni, 2003, 2009; Claro-Garcia & Shibatta, 2013), and in the area where Serra da Mesa dam was constructed (Bartolette et al, 2012)
This study investigated the ecology of M. paucisquamatus in the middle-upper rio Tocantins basin, an endemic fish currently threatened with extinction (Rosa & Lima, 2008)
Summary
Mylesinus includes three valid species (Eschmeyer et al, 2015), distributed in river systems of the Amazon basin and central Brazil. In the lower rio Tocantins, the species apparently persists in streams adjacent to the Tucuruí reservoir (Ribeiro et al, 1995; Santos et al, 2004; Nogueira et al, 2010) It was recorded in streams surrounding the Ecological Station of Serra Geral do Tocantins (Lima & Caires, 2011; Nogueira et al, 2011) and in the main channel of the rio Tocantins (Lucinda et al, 2007; Soares et al, 2009). These studies indicate that M. paucisquamatus is widely distributed throughout the basin, no study investigated patterns of occurrence and abundance along the rio Tocantins mainstem. It is known that a conspecific species, M. paraschomburgkii, feeds on aquatic plants, with predominance of Podostemaceae (Santos et al, 1997), so M. paucisquamatus may have a similar herbivorous diet
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