Hydropeaking effects of on the diet of a Neotropical fish community

Abstract

The impact of hydropeaking by dams is still poorly understood. Studying the diet of fish subjected to that variation allows us to test the following hypotheses: 1) seasonal and daily changes in river flow, causes changes in the use of the feeding resources; 2) species presenting larger differences in diet between seasons will be those with larger diet changes due to hydropeaking; 3) hydropeaking effects will be more evident in species feeding on items that can be more affected by variable flows. Fish diet collected from the Grande River, downstream from Itutinga Dam, in January and July 2010, was characterized by the feeding index (IA). NMDS, ANOSIM and SIMPER analyses were used to compare the diets under different hydropeaking and season. Relationship among diet dissimilarity between treatments was tested using Pearson Correlation. Seasonality and flow effects were not resulted in changes in the diet of species (hypothesis 1 rejected). In July, there was correlation of differences in the diet between stable and hydropeaking periods with the divergence caused by seasonality (hypothesis 2 accepted). The invertivores guild was the most affected by hydropeaking effects (hypothesis 3 accepted). This is the first study in Brazil that evaluates hydropeaking effects on ichthyofauna.O impacto da flutuação de vazão causada pelas barragens ainda é pouco entendido. Estudando a dieta dos peixes sujeitos à variação na vazão conseguimos testar as seguintes hipóteses: 1) mudanças sazonais e diárias na vazão do rio promovem mudanças no uso dos recursos alimentares; 2) espécies que apresentam maiores diferenças na dieta entre as estações serão aquelas com maiores mudanças causadas pela variação de vazão; 3) os efeitos da flutuação na dieta serão mais evidentes naquelas espécies que se alimentam dos itens potencialmente mais afetados pela variação de vazão. A dieta dos peixes coletados no rio Grande, à jusante da barragem de Itutinga, em janeiro e julho de 2010, foi caracterizada pelo Índice Alimentar (IA). NMDS, SIMPER e ANOSIM foram usados para comparar a dieta em diferentes períodos e estações. As relações entre a dissimilaridade das dietas entre tratamentos foram testadas utilizando Correlação de Pearson. Os efeitos da sazonalidade e flutuação não resultaram em mudanças na dieta das espécies (hipótese 1 rejeitada). Em julho, houve correlação das diferenças nas dietas entre os períodos de vazão estável e flutuante com a dissimilaridade provocada pela sazonalidade (hipótese 2 aceita). A guilda invertívoros foi a mais afetada pelo efeito de flutuação de vazão (hipótese 3 aceita). Este é o primeiro estudo no Brasil que avalia os efeitos da flutuação de vazão sobre a ictiofauna.

Feeding patterns, trophic structure and damming rivers effect: studies applied in freshwater environments in the Brazilian semi-arid region

“…Fish can improve their diet using the most energetic resources or through the consumption of food items with greater availability in the environment (Macarthur and Pianka 1966), which will depend on the fish's ability to seek, detect and ingest the prey (Abelha et al 2001). The diet can still be altered when fishes explore a new region in the environment (Gandini et al 2014). Due to spatial and seasonal modifications of the habitat, considering that distinct locations and periods have different abiotic and biotic conditions (Abelha et al 2001) and from opportunistic behavior, from substituting scarce items for others abundant (Davies et al 2008).…”

“…The excessive reduction of the level of the water of the reservoirs is a problematic that calls attention, because with the low level can cause an impact in the coastal region and in its surroundings, which can result in loss of the coastal zone, nursery and refuge for juveniles, with resulting loss of biodiversity (Winfried 2004). According to Gandini et al (2014), the impact of the flow fluctuation caused by dams is still poorly understood. Some authors demonstrate the effects of flow oscillations on the abiotic variables and the attributes of the fish assemblages, which influences their composition, abundance (Petry et al 2013), feeding and trophic structure (Corrêa et al 2009).…”

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

“…Study the diet and fish food interaction provides ecological information, such as the mechanisms that allow the coexistence and exploitation of resources by several species (Goulding, 1980), as well as to understand the behavior of species in the face of changes in environmental conditions and food availability (Silva et al, 2012b). Thus, studies on the diet of fish are of great importance because they are directly related to obtaining energy and help to understand the activities involved in the development, growth, reproduction and maintenance processes of the organism (Gandini et al, 2014;Bonato et al, 2012;Ribeiro et al, 2014). The variation of the water level at which the reservoirs are submitted annually is another relevant aspect related to the trophic structure, which can result in changes in the fish diet, once that the hydrological routes affect the food resources availability (Santos et al, 2014).…”

Feeding patterns, trophic structure and damming rivers effect: studies applied in freshwater environments in the Brazilian semi-arid region

“…The excessive reduction of the level of the water of the reservoirs is a problematic that calls attention, because with the low level can cause an impact in the coastal region and in its surroundings, which can result in loss of the coastal zone, nursery and refuge for juveniles, with resulting loss of biodiversity (Winfried 2004). According to Gandini et al (2014), the impact of the flow fluctuation caused by dams is still poorly understood. Some authors demonstrate the effects of flow oscillations on the abiotic variables and the attributes of the fish assemblages, which influences their composition, abundance (Petry et al 2013), feeding (Medeiros et al 2014) and trophic structure (Corrêa et al 2009).…”