Abstract
Aiming to characterize aspects of the trophic ecology of Loricariichthys melanocheilus in the Ibicuí river, bimonthly samples were taken in lotic and lentic ecosystems. Fish were caught and fixed in 10% formalin and dissected for stomach content analysis. Items were identified to the lowest taxonomic level possible. Stomach fullness (SF), repletion index (RI) and intestinal quotient (IQ) were estimated. Diet was assessed by the frequency of occurrence and the volumetric method, combined to obtain a Alimentary index. Feeding activity was analyzed with mean values of SF, RI and vacuity index (VI), which represents the percentage of empty stomachs. These parameters were compared seasonally, spatially, and according to the circadian rhythm. The main items in the trophic spectrum of L. melanocheilus were detritus, sediment, plant organic matter, nematodes, micro crustaceans (Copepoda, Cladocera) and insects (Diptera, Trichoptera, Ephemeroptera and Odonata). No environmental or seasonal variations were found for the consumed items. Feeding activity showed seasonal and environmental variations according to RI but did not significantly change according to SF. The IQ was 1.51, and showed seasonal variations, indicating changes in the diet.
Highlights
Studies on feeding are of fundamental importance to all organisms, under any conditions
Sediment, plant organic matter (POM) and nematode had a frequency of occurrence higher than 50%, and these were considered the most important food items in the L. melanocheilus diet, due to the higher frequency recorded and for having the highest volumetric percentages (Figure 2)
Some items were consumed only in certain periods of the year, and only detritus, sediment, other invertebrates (OI), Copepoda, Cladocera, POM and algae were ingested throughout the year (Table 2)
Summary
Studies on feeding are of fundamental importance to all organisms, under any conditions. A full understanding of the behavior of a species, regarding reproduction, growth, mortality, birth rate and migration, among other aspects, requires knowledge about its food needs (Andrian & Barbieri, 1996). Loricariichthys melanocheilus, known as “cascudo-viola”, or armored catfish, was recently described by Reis and Pereira (2000) for the Uruguay river and Paraná river basins, Rio Grande do Sul State. It is distinguished from other species mainly because of the caudal peduncle not greatly compressed and straight in the lateral view, and the Maringá, v. According to the same authors, it is a species very common in the lower and middle Uruguay river and in the lower Paraná river, either in streams or large rivers, usually associated with sandy and muddy bottom
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