Feeding ecology of stream-dwelling Characidae (Osteichthyes: Characiformes) from the upper Tocantins River, Brazil

Abstract

ABSTRACT. In this contribution we studied the trophic ecology of four Characidae species from the Cavalo Stream, upper Tocantins River, considering diet overlap and trophic niche breadth. The diet of the four species was composed of adult and immature insects, both autochthonous and allochthonous in origin. Autochthonous items dominated the diet of Moenkhausia dichroura (Kner, 1858), Bryconamericus sp., and Creagrutus atrisignum Myers, 1917. By contrast, allochthonous items were dominant in the diet of Astyanax bimaculatus (Linnaeus, 1758). Trophic niche breadth varied among species, with the highest value recorded for M. dichroura (0.48), followed by Bryconamericus sp. (0.39), A. bimaculatus (0.33) and C. atrisignum (0.29). Similarity analysis revealed two groups with different patterns of food preference. The first group was composed of insectivorous and the second by omnivorous species. The overlap in food items consumed by the four species studied was high. We suggest that resources are not limited in this stream and that competition might not be regulating these populations. This is one more case corroborating the general pattern registered for Tropical environments, where resource partitioning and specialization are responsible by the organization of fish communities.

Diet and ecomorphological relationships of an endemic, species-poor fish assemblage in a stream in the Iguaçu National Park

“…This is verified by the presence of (i) a considerable amount of terrestrial insects (Hymenoptera and Coleoptera), seeds, and plants, which attests to the contribution of the riparian vegetation to the input of organic matter to the system (Uieda & Pinto, 2011;Casatti, 2010;Moraes et al, 2013); (ii) the presence of organisms such as Ephemeroptera, Trichoptera, Plecoptera and Decapoda (Aeglidae) that are considered to be bioindicators of environmental quality and the structural complexity of the river bed (Bispo et al, 2006;Bagatini et al, 2012;Silva et al, 2012). In these context, the results about fish's diet, indicate that the Jumelo stream may used as a possible reference environment (sensu Ferreira & Casatti, 2006) for comparisons of trophic ecology between fish communities in impacted versus nonimpacted environments.…”

Does the oscillation of the water volume of the reservoir influence in the same way in fish diet?

“…Although the ichthyofauna of the reservoirs are mainly maintained by food of autochthonous origin, the allochthonous resources, are also representative parts in the energy input to the aquatic ecosystem, because provide different sources of food (vegetal/animal) for the maintenance and functioning of the fish communities (Moraes et al, 2013). The changes in the diet of the insectivorous guild between May and November may be due to water volume variations in the reservoir, once that in May the largest water volume was recorded in the reservoir, and in November, where was recorded one of the smaller water volumes.…”

“…During the rainy season occurs flooding of land areas, expanding the aquatic environment and originating new habitats for feeding, at which fish often transit, strongly influencing the food type consumed (Moraes et al, 2013), the opposite occurs during the dry, with the reduction of the water volume. Besides, the stored water in reservoirs suffers constant changes in their volume, mainly by the evaporation process, as in the semiarid regions where it is estimated that about 40% of the accumulated water is lost by evaporation (Meireles et al, 2007).…”

Neutral theory of biodiversity: Controversies and a transvaluation of species conservation

“…Em trabalho analisando a sobreposição de dieta e amplitude do nicho trófico de quatro espécies de Characiformes em um córrego na bacia do rio Tocantins, Moraes et al (2013) consideraram que essas espécies possuem recursos ilimitados e que na área amostrada a competição não possui um papel na estruturação dessa comunidade de peixes, provavelmente tendo sido estruturada de forma estocástica, como previsto pela teoria neutra.…”