Diet and trophic structure of the fish assemblage in the mid-course of the Teles Pires River, Tapajós River basin, Brazil

Abstract

This study was carried out in a section of the middle course of the Teles Pires River, a clear water river that drains ancient and highly eroded geological formations, and where five hydropower plants are planned or in construction. In this study we tested the hypothesis that local fish fauna is mainly sustained by autochthonous food resources, with modest changes in the trophic structure of fish assemblages along the hydrometric cycle. Sampling was performed every three months between July 2008 and May 2009 at seven sites distributed along a 50-km section of the river. Piscivores was the most representative group in terms of biomass, abundance and species richness, followed by herbivores, insectivores and omnivores. The trophic structure did not change significantly during the hydrometric cycle, only omnivores showed significant temporal variation in abundance. The main food resources consumed by the ichthyofauna were of autochthonous origin, mainly immature aquatic insects and fish. Eight of 34 species showed temporal variations of the food resources consumed. Our results corroborate the hypothesis that the fish fauna of large, clear water rivers can be sustained by autochthonous resources. This contributes to understanding some determinants of fish production in large Neotropical rivers. Este estudo foi desenvolvido em um trecho do curso médio do rio Teles Pires, um rio de águas claras que drena regiões de terreno geologicamente antigos, e onde cinco usinas hidrelétricas estão previstas ou em construção. Dado a transparência da água e as características do terreno nos hipotetizamos que a fauna de peixes local é principalmente sustentada por recurso autóctone e com alterações pouco significativas na estrutura trófica ao longo de um ciclo hidrométrico. As amostragens foram realizadas trimestralmente entre julho/2008 e maio/2009 em sete pontos dispostos ao longo de um trecho de cerca de 50 km do rio. Piscívoros foram os mais representativos em biomassa, número de exemplares e riqueza de espécies, seguidos pelos herbívoros, insetívoros e onívoros. Não houve mudança significativa na estrutura trófica da assembleia ao longo do ciclo hidrométrico, apenas onívoros apresentaram significativa variação temporal na abundância. Os principais recursos alimentares utilizados pela ictiofauna foram de origem autóctone, sobretudo insetos imaturos e peixes. Oito de 34 espécies apresentaram variação temporal na dieta. Os resultados corroboram a hipótese de que grandes rios de água clara podem ser sustentados majoritariamente por recursos autóctone. Desta forma, este estudo contribui para a compreensão de alguns fatores determinantes da produção secundária em grandes rios Neotropicais.

Mercury concentrations in fish and human health assessment in preflood phase of a hydro dam in Teles Pires River, Southern Brazilian Amazon

“…Thus, differences in mercury accumulation found in these fish species in this study may be related to morphological differences, life cycle, and food items of each species (Goulding, 1980;Terra et al, 2008). Because bioaccumulation, defined as increase in mercury concentrations over life of an organism, may not be the main factor that explains increase in mercury concentrations in Amazonian fish (Pouilly et al, 2012), studies on diet of these species show that in Teles Pires River basin these species are piscivorous predators of small caracids (Dary et al, 2017).…”

Survey of fish species from the Lower Roosevelt River, Southwestern Amazon basin

“…The total number of species found in the present study is in accordance with other studies in the Amazon River Basin. Some studies recorded 67 fish species in the Tapajós River (Keppeler et al, 2016), 86 species in the Purus River (Anjos et al, 2008), 90 species in the Juruá River (Silvano et al, 2000), 90 species in the Teles Pires River (Dary et al, 2017), 133 species in the Madeira River Basin (Camargo & Giarrizzo, 2007), 148 species in the Xingu River (Fitzgerald et al, 2017) and 160 species in the Guariba River (Pedroza et al, 2012). The Amazon River Basin contains the highest fish species diversity of any region on earth (Reis et al, 2003).…”

Quantifying shortfalls in the knowledge on Neotropical Auchenipteridae fishes

“…The lack of geographic coverage can also affect the knowledge about within-species variation of trophic habits, as the frequency of feeding on different sources can be highly influenced by where fishes are caught. For instance, Tocantinsia piresi showed carnivorous and frugivorous habits in two different Amazonian river basins (compare Mérona, Santos, & Almeida, 2001with Dary et al, 2017. Indeed, species with larger distributions (e.g.…”