Abstract
Tilapias are fish originally from Africa which nowadays are commercially bred in almost 100 countries, being one of the most commercially bred species in the world. In this work the trematode population of the monogenoidea group present in the branchiae of Nile tilapias bred in 4 net-ponds with volume of 4 m3 each, was monitored during 5 months. The juvenile fish, presenting initial average weight of 37.65 g originated from other piscicultures, were stocked in the density of 250 animals.m(-3) and monthly monitored until their commercialization, with final average weight of 485.4 g. The prevalence of these ectoparisites was high, between 90 and 100% in all months. The highest values of average intensity of infestation--AII and average abundance of infection--AAI occurred during the 2 first months of captivity, presenting a new increase in the last month of breeding. The only monogenoidea group present in the branchiae of the animals examined belonged to the Dactylogyridae family. The values of the dissolved oxygen, temperature, pH, nitrite and ammonia were within normal rate. In these conditions there were no significant differences between the relative condition factor--Kn among the parasited and non-parasited animals and also in the different levels of infestation, showing that, in these breeding conditions, the relationship parasite-host-environment presented itself in balance without causing great harm to the animals.
Highlights
Tilapias are fish originally from Africa which nowadays are commercially bred in almost 100 countries, being one of the most commercially bred species in the world
Práticas de manejo adotadas em sistemas de cultivo intensivo de peixes, como altas densidades de estocagem, elevados níveis de arraçoamento, frequente remoção e reestocagem de peixes, entre outros, podem exercer impactos negativos sobre o bem-estar geral dos peixes, diminuindo a resistência dos mesmos (KUBTIZA; KUBTIZA, 1999)
The values of the dissolved oxygen, temperature, pH, nitrite and ammonia were within normal rate. In these conditions there were no significant differences between the relative condition factor – Kn among the parasited and non-parasited animals and in the different levels of infestation, showing that, in these breeding conditions, the relationship parasite-host-environment presented itself in balance without causing great harm to the animals
Summary
O presente trabalho foi realizado junto a uma piscigranja de tilápias-do-nilo criadas em sistemas de tanques-rede, localizada na represa de Capivara, bacia do rio Paranapanema, junto ao município de Sertaneja, PR. Apresentando peso médio inicial de 37,65 g, foram estocados, no dia 13 de novembro de 2002, em oito tanques-rede com malhas de 3/4 de polegadas e volume de 4 m3. A densidade de estocagem inicial foi de 250 peixes.m–3. Após a estocagem dos peixes, sortearam-se quatro tanques-rede para o monitoramento dos animais até o dia 8 de abril de 2003 quando foram comercializados com peso médio final de 485,4 g. Os peixes estocados nos tanques-rede foram alimentados com ração comercial extrusada apresentando, na fase inicial de dois meses de criação, granulometria de 4,5 mm (peixe 38%) e, durante a fase final de três meses, uma ração de 6,0 mm (peixe 30%) de acordo com níveis de garantia fornecida pelo fabricante (Tabela 1)
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