Monogenoidea (Dactylogyridae) em tilápias-do-nilo cultivadas sob diferentes densidades de estocagem em tanques-rede

Abstract

The prevalence and infection intensity of Monogenoidea in Nile tilapia (Oreochromis niloticus) cultivated under different stocking densities in 4m3 cages were evaluated. The experiment was designed in sample random sampling with four treatments - densities (D) of D1=250, D2=300, D3=350, and D4=400 fish/m3-and three repetitions, using 360 fish captured and analyzed during the period from February to June 2003. Physiochemical parameters of the water were monthly monitored. Prevalences of 52.8; 62.5; 69.4; 83.3; and 58.3% and parasitic mean intensities of 112.8; 65.7; 274.0; 97.8; and 100.2 Dactylogyrus sp. (Monogenoidea: Dactylogyridae) were observed. No relationship between the prevalence and infection intensity with the cultivation density was found. However, quadratic effect was verified (P<0.05) related to the parasitic intensity in function of the month. High mean intensity of infection (274) and high prevalence (83.3%) were verified in the months in that the temperature and the transparency of the water oscillated below the recommended limits for the thermal comfort and well-being of tilapia.