Trophic ecology of the Neotropical tolerant fish Corydoras paleatus under the influence of contrasting environmental conditions in a prairie stream.

Andrea Bertora,María S Fontanarrosa,Juan J Rosso,Fabián Grosman,Pablo Sanzano

doi:10.1590/0001-3765202120200981

Abstract

Worldwide, land use changes and urbanization affect habitat and biota in streams, drastically disrupting environmental conditions and biotic interactions. We evaluated the trophic ecology of the tolerant fish Corydoras paleatus in a prairie stream with contrasting environmental conditions intimately aligned with different nearby land uses. Gut analyses was conducted at three stream reaches with contrasting ecological attributes regarding water quality, habitat structure and riparian condition. A total of 231 guts were analyzed and 15 prey items identified. A significant variation in composition and structure of the dietary assemblage, niche breadth and feeding patterns of C. paleatus under different environmental conditions was observed. Psychodidae prevailed in most deteriorated environmental conditions and Chironomidae, followed by nematodes, in stream reaches where environmental conditions improved. Maximum niche breadth and a larger proportion of generalist individuals were found at the most deteriorated site. Conversely, the proportions of specialized individuals were slightly higher at sites with better ecological conditions. Psychodidae and mineral fragments were positively correlated with the most detrimental conditions, while filamentous algae prevailed where these conditions improved. Overall, good evidence suggesting that trophic ecology of a tolerant species is affected by local environmental conditions in water quality, habitat structure and riparian corridor was observed.

Highlights

Freshwater ecosystems face a major threat derived from the development of human populations in their drainages (Albert et al 2020), where streams are vulnerable (Walsh et al 2005)
Habitat structure and riparian conditions in streams are largely influenced by nearby land uses, we argued about the eventual role of human activities in the surrounding landscape on the trophic ecology of a tolerant fish species
In the stream site exposed to agriculture, water quality was similar to livestock-exposed site, habitat structure was characterized by the presence of macrophytes and riparian vegetation showed mainly herbaceous development, high bank stability and open canopy

Summary

Introduction

Freshwater ecosystems face a major threat derived from the development of human populations in their drainages (Albert et al 2020), where streams are vulnerable (Walsh et al 2005). Several aspects of water chemistry, habitat structure, channel morphology, macrophytes coverage, substrate composition and riparian vegetation are drastically affected (Platts 1979, Paul & Meyer 2001, Walsh et al 2005, Moss 2008, Arocena et al 2018, O’Callaghan et al 2018) Their effects on the ecological integrity of the streams generate direct and indirect impacts on different aquatic communities, including the composition and structure of fish communities (Karr 1981), and population aspects, such as trophic ecology (Aranha et al 1998, Ferreira et al 2012, Dala-Corte et al 2016). The diet and trophic behavior of the different fish species have being altered by changes of environmental conditions imposed by nearby land uses (Aranha et al 1998, Grether et al 2001, Ceneviva-Bastos & Casatti 2007, Ferreira et al 2012, Manna et al 2012, DalaCorte et al 2016)

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