Variação nictemeral e espacial da comunidade zooplanctônica em uma piscicultura intensiva no Reservatório de Pedra do Cavalo, Ba

Abstract

The creation of tilapia in net cages has been developed in many reservoirs in Brazil. The study of zooplankton organisms is important because respond to different environmental impacts. The objective of this study was to investigate the influence of fish ponds in the distribution of the zooplankton community. This study was conducted at the fish farm in Pedra do Cavalo Reservoir, Bahia state. Samples were collected at three points in February 2011. The physical and chemical variables of water and zooplankton samples qualitative and quantitatively were analyzed. The results were: maximum temperature of 30.8 °C, the lower dissolved oxygen was 4.9 mg L-1, 17.8 NTU turbidity maximum, maximum transparency of 2.1 m and the maximum electric conductivity of 333, 3 μS.cm 1. Chlorophyll ranged from 27.6 to 31.0 microg.L-1. Zooplankton community was represented by Rotifer (55% of total), Cladocera (11%) and Copepoda (33% of total). In points 2 and 3 were recorded greater amount of Brachionus and Diaphanosoma compared to point 1. In time 23:00 and 7:00 hours was found more zooplankton. The results indicate that net cages may have influenced the dynamics of zooplankton community because Brachionus and Diaphanosoma, bioindicators of trophic state, were found constantly in the points.