Habitat heterogeneity on feeding habit of two sympatric and congeneric characidae fishes in two tropical reservoirs

Abstract

ABSTRACT. Food fl exibility and omnivory are important features pronounced in Neotropical freshwater fi sh species, particularly for Astyanax species. Traditionally most fi sh diet resources are known to be originated in the aquatic environment, however recent studies have pointed to the importance of allochthonous sources. Besides, the colonization of macrophytes, common at several tropical reservoirs, may enhance insectivory in fi sh diet expanding or concentrating the area of available resources for feeding. Here we employed stomach contents analysis of two sympatric Astyanax species to access the importance of habitat diff erentiations as spatial complexity in two tropical reservoirs with diff erent environmental features. The NMDS analysis indicated separation in the diet of these species between reservoirs (Stress= 8.28%). Additionally, analysis of variance revealed a signifi cative diff erence in the volume of food itens ingested between the reservoirs (Anova one-way F(1, 132)=4.4446; p= 0.037). This points out the importance of environmental conditions on the composition of the diet of fi shes. This study highlighted the insectivorous feeding habit of Astyanax species and revealed diff erent feeding strategies between sympatric fi shes despite high niche overlap in both environments. Habitat heterogeneity increasing food resources availability plays an important role in the diet strategy of these Astyanax species and on their constant maintenance in the two diff erent reservoirs.KEYWORDS. Feeding resources, land-water ecotone, trophic ecology, Astyanax aff . bimaculatus, Astyanax parahybae. RESUMO. Heterogeneidade de habitat no hábito alimentar de duas espécies simpátricas e congenéricas de peixes caracídeos em dois reservatórios tropicais.A fl exibilidade alimentar e onivoria são características das espécies de peixes de água doce neotropicais, especialmente em espécies de Astyanax. Tradicionalmente a maioria dos recursos na dieta de peixes é reconhecidamente originária do ambiente aquático, porém estudos recentes têm apontado para a importância das fontes alóctones. Além disso, a colonização de macrófi tas, comuns em vários reservatórios tropicais, pode melhorar os aspectos de insetivoria na dieta dos peixes expandindo ou concentrando a área disponível para a alimentação. Aqui analisamos o conteúdo estomacal de duas espécies de Astyanax simpátricas para avaliar a importância das diferenças de habitats, como a complexidade espacial, em dois reservatórios tropicais com diferentes características ambientais. A análise NMDS indicou separação na dieta destas espécies entre reservatórios (stress = 8.28%). Além disso, a análise de variância revelou uma diferença signifi cativa no volume de itens alimentares consumidos entre os reservatórios (Anova one-way F (1. 132) = 4,4446; p = 0.037), salientando a importância das condições ambientais na composição da dieta de peixes. O estudo destacou o hábito alimentar insetívoro das espécies de Astyanax e revelou diferentes estratégias de alimentação entre esses peixes ...

Water-level controlled reservoir as refugia for waterbirds in an urban landscape

“…and fluvial islands (Kameníková and Rajchard 2013). These nests were not observed in the study area, which is certainly related to the prevalence of pasture areas and residences around the reservoir (Lopes et al 2016). Therefore, despite the availability of food resources, there is a possible lack of nesting substrates for most species in the reservoir.…”

“…This trend was found elsewhere (Rodrigues and Michelin 2005;Silva et al 2017;Aikins et al 2018) and is often related to decreases in water level, which facilitates food capture (Rubim 2013). However, this fact does not explain the variation reported for the Santana Reservoir, because water levels are mechanically controlled with maximum daily variations of 1.5 m (Lopes et al 2016). The lowest abundance during the rainy season, when most birds breed, is possibly due to reproductive displacement (Sick 1997).…”

“…The average temperature is 20.5°C, ranging from 16.6°C in July to 23.9°C in February, with the dry season lasting from April to September, and the rainy season from October to March. Seasonality does not influence reservoir water levels since these are operationally controlled, with a maximum variation of 1.5 m per day (Lopes et al 2016).…”

“…The reservoir is eutrophic, suffering high degrees of human impact and displaying a prevalence of surrounding deforested areas used for ranching (Lopes et al 2016). Due to the constant entry of organic matter from anthropogenic activities, macrophyte proliferation is observed along the reservoir.…”

Zooplankton community attributes in an oligo-mesotrophic reservoir: A comparative study of two sampling strategies

“…Besides that, the low turbidity at the dam can be suggested to increase fish predation on zooplankton, explaining a lower total abundance of the community in the water column. Several authors have already reported an important consumption of zooplankton by fish in Lajes Reservoir (Dias et al 2005, Ferreira et al 2013, lopes et al 2016.…”