Structure of the littoral fish assemblage in an impounded tributary: the effects of macrophytes presence (subtropical region, Brazil)

S Hermes-Silva,E Zaniboni-Filho

doi:10.1590/s1519-69842012000300011

Abstract

To evaluate the effects of macrophytes presence in the structure of littoral fish assemblages in the littoral zone, monthly samples were collected from September, 2006 to August, 2007 in an impounded tributary of the Itá Reservoir, the Fragosos River, located in the Upper Uruguay River Basin. Fish were collected using a beach seine and sampling was conducted in the littoral zone inside a macrophyte stand and in an area with no macrophytes. A total of 5,191 fish were captured during the study period. Fish assemblage attributes (fish abundance, species richness, and diversity) varied significantly between sampling months and areas. The abundance of Astyanax cf. bimaculatus, Astyanax fasciatus, Geophagus brasiliensis, and Gymnotus carapo also varied significantly between sampling months and areas. Detrended Correspondence Analysis showed a clear spatial segregation at the first axis and a slight temporal segregation at the second axis. These results were confirmed by Multiple Response Permutation Procedure analysis. Apparently, the presence of the aquatic macrophytes is not the only factor influencing the distribution of littoral fish assemblages in the Fragosos River. Littoral fish seem to be taking advantage of low- to medium-sized macrophyte stands, but few species used maximum-sized stands.

Highlights

The importance of the littoral zone to aquatic organisms has been demonstrated in many aquatic systems (Vono and Barbosa, 2001; Lewin et al, 2004; Tolonen et al, 2005)
To evaluate fish assemblage structure associated with a macrophyte stand at the Itá Reservoir, located in the Upper Uruguay River, we selected the Fragosos River, an impounded tributary of the lower portion of the reservoir
Of all the species and assemblage attributes analyzed, only G. carapo seemed to be directly influenced by the presence of the E. crassipes

Summary

Introduction

The importance of the littoral zone to aquatic organisms has been demonstrated in many aquatic systems (Vono and Barbosa, 2001; Lewin et al, 2004; Tolonen et al, 2005). Aquatic macrophytes add complexity to aquatic systems because of their plant morphology (the structures of roots, stems, and leaves), creating a unique substrate for macroinvertebrate and zooplankton fixation (Dibble and Thomaz, 2006) and promoting an enhancement of food availability for fish (Casatti et al, 2003; Dibble and Thomaz, 2006; Pelicice and Agostinho, 2006). They provide refuge from predators to young and small adult fish (Meschiatti et al, 2000; Agostinho et al, 2003, 2007; Neiff et al, 2009). The high complexity provided by the presence of macrophytes can promote higher fish diversity, abundance and species richness (Petry et al, 2003; Pelicice et al, 2005; Agostinho et al, 2007; Dibble and Pelicice, 2010), influencing the fish assemblage structure of littoral habitats.

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Results

Conclusion