Influence of fish farming in net cages on phytoplankton structure: a case study in a subtropical Brazilian reservoir.

Ecr Bartozek,Nc Bueno,Lc Rodrigues

doi:10.1590/1519-6984.21912

Abstract

This study investigated the enrichment influence due to fish farming in net cages on the phytoplankton composition, density and diversity in two arms of a subtropical reservoir (Salto Caxias, Paraná). There were no statistically significant differences in the phytoplankton composition and diversity, as well as for concentrations of nutrients among the handled treatment. The density values were higher during the summer. Richness and Shannon diversity values were low during the study period. The equitability values were high during the winter and low in the summer. Variations of phytoplankton community and nutrients were mainly influenced by seasonality. The absence of significant differences between the treatments was probably due to the small number of net cages and fish used, as well as to the hydrodynamics of the studied environments, which are influenced by upstream rivers inflows.

Highlights

IntroductionDuring intensive cultivation in net cages, large amounts of organic matter, from feedstuffs used in feeding and from fish excreta, are directly released in the aquatic environment (Alves and Baccarin, 2007; Santos et al., 2009)
In Brazil, fish cultivation in net cages is a relatively recent activity that started in the 1980s, been introduced in the country, mainly, to generate employment and income, and has been growing substantially in recent years and receiving governmental incentives (Alves and Baccarin, 2007; Ayrosa et al, 2008)
The Iguaçu River is formed by the union of Irai and Atuba rivers in Curitiba city, and travels around 1,320 km following its course to debouch on Paraná River, in the city of Foz do Iguaçu (Paraná, 2010)

Summary

Introduction

During intensive cultivation in net cages, large amounts of organic matter, from feedstuffs used in feeding and from fish excreta, are directly released in the aquatic environment (Alves and Baccarin, 2007; Santos et al., 2009). Such activity can increase the concentration of nitrogen and phosphorus in the water column, leading to the eutrophication of the system (Diaz et al, 2001; Figueredo and Giani, 2005; Alves and Baccarin, 2007).

Objectives

Methods

Results

Conclusion