Variação anual de ovos de larvas de peixes no Médio Rio Uruguai em Porto Vera Cruz (RS/Brasil)

Abstract

The present work of conclusion of course has as its theme the temporal distribution of eggs and larvae in Porto Vera Cruz (RS/Brazil). Studies on Ichthyoplankton in the Middle Uruguay are almost non-existent, which motivated the creation of this project, which aims to assess the temporal distribution of eggs and larvae in the Middle stretch of Uruguay and its relationship to environmental variables. The sampling area is in the Uruguay River, located in the city of Porto Vera Cruz, Rio Grande do Sul. The collections were made monthly in July 2015 period to June 2016, at night. Each collection had 15 minutes duration, being carried out four collections per month. In all points has been used two plankton nets conical-cylindrical format, in addition to equipment for measurement of environmental variables. In the laboratory, the samples were sorted to separate the Ichthyoplankton with the aid of a stereoscopic microscope in increased 10 times. To evaluate the differences of the arithmetic mean of eggs and larvae and larval stages over time, was applied a unifatorial analysis of variance (one-way ANOVA), having as its factor, the months of the year. For the assessment of the four most important taxa, we applied ANOVA protected Protocol. To assess the correlation of environmental variables, with plenty of eggs, larvae, their larval stages, and of the four taxa of greater relevance, Pearson correlation was used. To get a dimensionality reduction of environmental variables was applied principal component analysis (Principal Components Analysis; PCA). During the study period were captured 57 eggs and 933 larvae. The four species had a higher abundance were the Pimelodus maculatus, Bryconamericus iheringii, Iheringichthys labrosus and Pimelodus albincans, was also recorded the presence of species of long migration, such as Brycon orbignyanus, Luciopimelodus pati and Pterodoras granulosus. The eggs were captured between the months of September and December, its peak was in October and November. The larvae were present between the months of September through February, and in April, having its peak in November. The present study allows us to conclude that the reproduction of the fish in the Middle Uruguay is seasonal with reproductive activity in spring and summer being the peak in November, when it was verified increase in temperature and the high water level. Uruguay midfielder, seems to work as a nursery place for migratory species and even threatened with extinction.