Abstract
Abstract: We examined size-related and seasonal changes in the diet of the peacock bass Cichla kelberi in a tropical lowland reservoir in southeastern Brazil over three hydro-climatic seasons: summer (high rainfall and temperature), winter (low rainfall and temperature), and late spring (increasing rainfall and temperature) during two years (2006-2007). The tested hypothesis is that this non-native predator fish changes diet during the subadult and adult phases and among seasons to adapt in new colonized environment. Fishes of the families Clupeidae (Platanichthys platana), Characidae (Astyanax spp.) and Cichlidae (Cichla kelberi) were the most important food items, followed by insects of the order Odonata. Cannibalism was also recorded for the largest individuals. A significant size-related change in diet was found with the smallest individuals (Total Length, TL < 20 cm) preying mainly on fishes, whereas the larger individuals (TL > 30 cm) preyed mainly on Odonata. The niche breadth increased during growth, with the largest individuals having a diet more evenly distributed among the available resources. No significant seasonal differences in diet composition were found, but stomachs with higher degree of volume occupied by food were more frequent in late spring than in summer. Conversely, the highest niche breadth was found during the summer compared to the other seasons. Together, these observations suggest an efficient use of the available resources by this top predator in this new colonized system.
Highlights
Many rivers in southeastern Brazil have undergone considerable changes due to the construction of dams
Such seasons were already established in other studies (e.g. Azevedo et al 2016) and the database supporting this pattern is available from the Instituto Nacional de Meteorologia (INMET), available at http://www.inmet.gov.br/html/clima.php#
The Cichlidae family was represented by C. kelberi, indicating cannibalism habit
Summary
Many rivers in southeastern Brazil have undergone considerable changes due to the construction of dams. The non-native species are, in many cases, more tolerant to the lentic conditions than the previously native lotic fish fauna (Hoeinghaus et al 2009, Araújo et al 2013). Introduced species can affect the functioning of ecosystems by changing trophic relationships, besides presenting other deleterious effects (Adams 1991, Meffe et al 1997, Marchetti 1999, Kati et al 2015). These changes may have important economic and ecological consequences (Gomiero & Braga 2003, Fugi et al 2008, Pelicice & Agostinho 2009). Non-native species can alter the functioning of local ecosystems by intensifying predation pressure on native species, or by searching for other prey that are not used by native predators (Zavaleta et al 2001, Laxson et al 2003)
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