Effect of drought and variation in the space of individuals in abundance of trophic guilds ichthyofauna in a reservoir in the Brazilian Semiarid

Abstract

The individual’s abundance that compounds the fish trophic guilds may be governed by time and space changes, considering that different periods and places have different biotic and abiotic conditions. Thus, it was verified the effect of drought and spatial differences in the abundance of individuals in trophic guilds of fish in Pau dos Ferros reservoir, Rio Grande do Norte. Fish were collected at four points in the months of February, May, August and November 2012. After the capture, identification and biometrics, prey items from stomachs and intestines were identified and their volumes estimated. We calculated the Alimentary Index (IAi), and their values used to determine trophic guilds. Then it was verified similarity among species of trophic guild. The number of individuals that compound the guilds was used in a similarity matrix, and the results of this procedure have been ordered in multidimensional scaling analysis no metric (NMDS), to assess the temporal and spatial distribution of the guilds. The species were classified into four trophic guilds: insectivorous, detritivorous/iliophagous, herbivorous and piscivorous. Based on this classification it was found that the dry season and the structure of the collection sites favored the establishment of insectivorous guilds and detritivorous/iliophagous over the months and studied sites, since the reservoir Pau dos Ferros is a eutrophic environment and low depth with high primary productivity and greater availability of insects, debris and sediment.