Physical and chemical water parameters and Streptococcus spp. occurrence in intensive tilapia farming in the State of Espírito Santo, Brazil

Ruben Pablo Schocken-Iturrino,Maria Isabel Suhet

doi:10.4025/actascibiolsci.v35i1.11797

Abstract

This study evaluated the influence of intensive farming of tilapia on physical and chemical parameters and on the occurrence of Streptococcus spp. in the water of the lake and of cages. Throughout a year, monthly samplings were taken in the rainy and dry seasons for a year, at two sampling sites, lake and net cages. For the determination of water quality, physical and chemical water parameters were evaluated and compared to the standards established by Conama Resolution no. 357/2005. The presence of Streptococcus spp. in the water was determined by plating on blood Agar and biochemical screening. Mean values of water parameters were tested using the Kruskal-Wallis test comparing sampling sites and seasons. Ammoniacal nitrogen (ammoniacal-N), total phosphorus (total-P) levels and occurrence of Streptococcus spp. have increased in the water of the net cages. The mean values of several parameters have decreased during the rainy period, except for pH, temperature and ammoniacal-N. Total-P and dissolved oxygen levels, during dry and rainy periods, respectively, exceeded the standard established for freshwater class 2, recommended for aquaculture, which can be harmful to the fish. Therefore, constant monitoring of the physical,chemical and microbiological water parameters is recommended since the Juara lake is also used for recreational purposes.

Highlights

World tilapia production was 2,382,998 tons in 2008, and Brazil was ranked 6th with production of 96,000 tons (FAO, 2010)
The nomenclature adopted in this study was as follows: dissolved oxygen (DO), non-ionized form of ammonia (N-NH3); ammonium ion, the ionized form (N-NH4+), ammoniacal nitrogen refers to both nitrite (N-NO2-) and nitrate (N-NO3-), and total phosphorus(total-P)
Higher levels were observed in the net cage water, except for DO

Summary

Introduction

World tilapia production was 2,382,998 tons in 2008, and Brazil was ranked 6th with production of 96,000 tons (FAO, 2010). This high productivity is mainly due to the expansion of intensive farming characterized by monoculture, artificial feeding and high stocking density (SHOEMAKER et al, 2000). Biological Sciences intensive fish farming, nitrogen and phosphorous are considered as the main pollutants (BUENO et al, 2008; GUO et al, 2009). The high levels of nitrogen and phosphorous in the water trigger the eutrophication process, making the water quality inadequate for fish farming (GUO et al, 2009).

Methods

Results

Conclusion