Diet of Bryconops alburnoides and B. caudomaculatus (Osteichthyes: Characiformes) in the region affected by Balbina Hydroelectric Dam (Amazon drainage, Brazil)

Abstract

The study of fish diet and its interaction with the environment provides important data on ecology and behavior, as fish face varying environmental and food availability conditions. The aim of the present study was to determine the diet of Bryconops caudomaculatus and Bryconops alburnoides, as well as to assess its seasonal variation, within the area influenced by Balbina Hydroelectric Dam (BHD), in the Uatumã River (Amazon Basin, Brazil). Collections were carried out every two months from April 2005 to February 2007, using gill nets with mesh sizes ranging from 12 to 60 mm between opposite knots. Two methods were used for determining diet: frequency of occurrence and relative volume, which were used to calculate the alimentary index (IAi). Diet similarity between species was analyzed by applying the Morisita index. Bryconops alburnoides ingested 12 items and B. caudomaculatus 10, with a 59% similarity between ingested items. Terrestrial insects for B. alburnoides and immature insects for B. caudomaculatus were the main items in their diets, and therefore, they were considered insectivorous. The seasonal composition of the diet of B. alburnoides was influenced by environmental factors, and in spite of the dominance of immature insects, it had a significant number of terrestrial insects during the heavy rainfall periods.O estudo da dieta de peixes e sua interação com o ambiente fornecem importantes informações ecológicas e comportamentais das espécies frente às variações nas condições ambientais e de disponibilidade de alimento. Este estudo teve por objetivo determinar a alimentação de Bryconops caudomaculatus e Bryconops alburnoides e avaliar suas diferenças sazonais na área de influência da UHE Balbina, rio Uatumã, Amazonas. As coletas foram realizadas bimestralmente de abril/2005 a fevereiro/2007, utilizando-se redes de espera com malhas variando de 12 a 60 mm entre nós opostos. Foram utilizados dois métodos na determinação da dieta: freqüência de ocorrência e volume relativo, sendo ambos combinados no Índice Alimentar (IAi). A similaridade da dieta entre as espécies foi analisada aplicando-se o índice de Morisita. Ambas as espécies apresentaram a dieta diversificada. Bryconops alburnoides ingeriu 12 itens e B. caudomaculatus 10, com uma similaridade de 59% entre os itens ingeridos. Os insetos terrestres para B. alburnoides e os imaturos para B. caudomaculatus foram os itens que mais se destacaram nas dietas, portanto foram consideradas insetívoras. Fatores ambientais influenciaram na sazonalidade da composição da dieta de B. alburnoides, apesar dos insetos imaturos serem mais preponderantes na dieta da espécie, houve uma ingestão significativa de insetos terrestres nos períodos de maior pluviosidade.

Reproductive strategies of Amazonian stream fishes and their fine‐scale use of habitat are ordered along a hydrological gradient

“…The restriction of Bryconops to stream channel habitat may arise from low tolerance to hypoxia or from ecological constraints related to a reproductive strategy requiring medium‐to‐long‐distance dispersal of offspring (Winemiller, ). Alternatively, this restriction may be related to the feeding mode of Bryconops , which are highly dependent on large inputs of allochthonous food transported by the current, such as terrestrial insects (Silva, Ferreira & de Deus, ). Moreover, pond occupancy by Bryconops may be impaired by structural habitat features (e.g.…”

Dining out: Bryconops caudomaculatus jumps out of water to catch flies

“…Sazima (1986) and Sánchez et al (2003) found a greater impor tance of allochthonous food items in diet of B. melanurus. Whereas Silva (1993) described B. melanurus as benthic/nektonic, with autochthonous food items predominating in the diet, a similar result to that found by Silva et al (2008) to B. caudomaculatus. We believe that the time of the day that sampling is carried out may affect the food items found in stomach contents.…”

Feeding ecology of Dash-dot Tetra Hemigrammus belottii(Steindachner 1882) (Characiformes: Characidae) in the streams of the Urucu River basin, central Amazonia, Brazil

“…While a number of studies have recorded spatial and temporal variation in fish diets (Hahn et al 1992, Motta & Uieda 2004, Brandão-Gonçalves et al 2009, Lima & Behr 2010, no such pattern was recorded in H. belottii, probably related to the generalist behavior of the species, which appears to be typical of the characids (Bennemann et al 2005, Silva et al 2008, Brandão-Gonçalves et al 2009). However, the lack of variation may also be related to the abundance of resources in Amazonian streams (Knöopel 1970).…”