Abstract
ABSTRACT Diet, energy density (ED) and relative condition factor (Kn ) were used to investigate the energetic assimilation of the invasive fish Hemiodus orthonops under different environmental condition of the upper rio Paraná floodplain. Samples were taken in June and September 2013 and 2014. Nutrient content was determined for sediment. The diet was combined in the Food Index (IAi%), ED was expressed in Kcal/g of dry weight and Kn was calculated by: Kn = Wt/We, where Wt is the total weight and We the expected weight. Detritus/sediment prevailed in the stomachs of specimens from Ivinhema and Baia, while Algae was the main item in Paraná, reflecting the resource availability. ED and Kn from Ivinhema specimens were the greatest, consequence of the quality of food and lower spent on searching and handling food. The Paraná specimens showed lower ED values, but higher Kn values, due to algae consumption, a nutrient-rich resource. Baia presented high aluminum concentration on the sediment and the lower pH values, which contribute to reduce the nutritional value of the detritus and the ED and Kn values of their specimens. In conclusion, H.orthonops is capable to take advantage of the resources availability in the different environments, ensuring their establishment.
Highlights
Introduction of species in natural environments is one of the most serious threats to biodiversity (Clavero & García Berthou, 2005; Davis, 2009; Vitule & Prodocimo, 2012)
Food items that composed the diet of the species were: Algae (Zignemaphyceae, Cyanophyceae, Oedogonophyceae e Chlorophyceae), Detritus/sediment, Aquatic plant, Microcrustacean and Other organisms
Detritus/sediment and filamentous algae are the predominant items in the diet of H. orthonops from the upper rio Paraná floodplain as a whole
Summary
Introduction of species in natural environments is one of the most serious threats to biodiversity (Clavero & García Berthou, 2005; Davis, 2009; Vitule & Prodocimo, 2012). The success of invasive fish species has been linked to the deleterious effects of human activities (Taylor & Irwin, 2004; Leprieur et al, 2008) that promote greater temporal and spatial variability of physicochemical characteristics (Havel et al, 2005; Johnson et al, 2008) Such variability favors non-native species due to higher tolerance to changes in physicochemical characteristics and plasticity of life history traits such as diet and reproduction (Marchetti et al, 2004; Gutierre et al, 2014; Santos et al, 2014). Its preserved stretch is mainly represented by Neotropical Ichthyology, 14(1): e150164, 2016
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