Does seasonality and pool connectivity influence fish trophic ecology in knickzone habitats?

Macrophytes banks as potential fish nursery areas in small hydropower reservoirs

“…The number of taxa we found, at least 20 species, is comparable to other studies that also searched for fish inside macrophyte banks in Brazilian rivers and reservoirs, which varied between 22 to 26 species, but with a much higher sampling efforts -5 to 50 times more captures (Pelicice et al, 2008;Dibble & Pelicice, 2010;Hermes-Silva & Zaniboni-Filho, 2012). In terms of composition, it is also important to mention that we sampled fish species of all orders occurring in this river (Oliveira et al, 2016;Brambilla et al, 2019;Diniz et al, 2019), namely Characiformes, Siluriformes, Gymnotiformes, Synbranchiformes and Cichliformes. This mean that fish species with distinct evolutionary histories, reproductive biology, and ecological traits (Reis et al, 2003), are using, in some way or in some period of their life cycle, the macrophyte habitats.…”

“…The presence of small sedentary species, especially in the lotic compartment of Palmeiras reservoir, may be associated with the proximity Acta Limnologica Brasiliensia, 2021, vol. 33, e28 with a knickzone, located immediately upstream, where 82% of the species were of small size, representing 98% of total abundance observed in this macrohabitat (Brambilla et al, 2019). The higher abundance of individuals of the Synbranchidae family in the macrophyte banks, as well as the presence of the order Gymnotiformes, can be explained by the adaptations they have such as the elongated body shape, easily camouflaged between plants, insectivorous feeding behavior, and tolerance to low oxygen concentrations (Henderson & Hamilton, 1995;Crampton & Hopkins, 2005;Bulla et al, 2011).…”

“…It is a plateau river, with several rapids and small waterfalls in the upper section, becoming less turbulent with decreased water velocity in the lower section. Another distinctive characteristic of this river is the presence of several knickzones mesohabitats, bed rock (basaltic) platforms popularly known as "pedrais" (Brambilla et al, 2019;Ruocco et al, 2019). The river total length is 290 km, with its course entirely in the State of São Paulo (Paiva, 1982).…”

“…Two SHP's reservoirs were selected in our study, located in Sapucaí-Mirim River, north of São Paulo State, Brazil. This river basin has a diverse fish fauna, with at least 105 species (Oliveira et al, 2016;Brambilla et al, 2019;Diniz et al, 2019), and it is an important direct tributary of the Grande River, upper Paraná Basin. The fish fauna is mainly represented by small and medium-size species, with only three large-sized migrators (Oliveira et al, 2016).…”

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

“…The large variations in rainfall in these regions (Feow, 2018), occurring either seasonally (dry and rainy seasons) or due to short‐term events (episodic storm events), are additional factors that lead to flow and current velocity disparities at the scale of both mesohabitats and the entire landscape. These variables mediate the types of potential food resources carried into the river system and also lead to consequent changes in the dynamics of autochthonous resources and their availability (Brambilla, Uieda, & Nogueira, 2019; Brett et al, 2017; Giling, MacNally, & Thompson, 2015; Neves, Silva, Baumgartner, Baumgartner, & Delariva, 2018; Roach, 2013). This landscape and its underlying forces create a rich environment for niche partitioning or specialisation, which is generally expected to increase the number of species that can stably coexist there (Leibold, Urban, De Meester, Klausmeier, & Vanoverbeke, 2019; Schoener, 1974) and also potentially promote the evolution of morphological and ecological diversity.…”