Abstract
ABSTRACT Trophic structure of fish assemblages is one of the most sensitive indicators of changes in streams environments. Since it is crucial to understand the response of trophic groups to habitat alteration, our study aimed to address this research gap by assessing the influence of substrate composition, meso-habitat variability, and bank stability, on the richness, biomass, and number of individuals of carnivores, invertivores, omnivores, and herbivorous-detritivores. Using an electrofishing device, we sampled 13 Atlantic rainforest streams reaches in a degradation gradient, located in the upper Paranapanema river basin. Sample points were ranked using a physical habitat index. More pristine streams had high availability of twigs, trunks, rocks and boulders in the substrate, great meso-habitat variability, and the presence of roots, trunks, and rocks in the margins. Canonical correlations between habitat characteristics and trophic groups explained more than 90% of data variability. Richness and number of individuals of invertivores increased in more preserved stream reaches, while richness of carnivores and number of individuals of omnivores decreased. These results demonstrate that trophic structure varies according to level of degradation, and that invertivore richness represents the best indicator of fish trophic structure responses to physical habitat alterations in streams.
Highlights
The study of trophic structure is an important tool for evaluating fish assemblage structure (Angermeier, Karr, 1983; Nimet et al, 2015)
Hoplias malabaricus had the highest number of individuals and presented the highest biomass for the carnivore trophic group
Phalloceros reisi had the highest number of individuals, while Geophagus brasiliensis presented the highest biomass
Summary
The study of trophic structure is an important tool for evaluating fish assemblage structure (Angermeier, Karr, 1983; Nimet et al, 2015). Since environmental filters act by selecting assemblage species according to their traits, the effects of physical habitat characteristics on trophic structure may be a more accurate predictor than taxonomic composition (Teresa et al, 2016). Several habitat elements have been shown to influence fish assemblages in streams, including substrate composition and flow heterogeneity (Hugueny et al, 2010; Carvalho, TejerinaGarro, 2015). Channel morphology variables such as substrate, depth, and velocity alter trophic structure as large carnivores tend to predominate in large pools or streams (Schlosser, 1982). Cross et al (2013) showed that streams subjected to siltation, a form of environmental simplification in which there is Neotropical Ichthyology, 18(2): e190076 , 2020 scielo.br/ni | sbi.bio.br/ni
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