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This study evaluated seasonality in hematological parameters of Nile tilapia cultured in the state of Santa Catarina, southern Brazil. A total of 240 fish were examined during four seasons between April 2007 and March 2008 in three different fish farms. After being anesthetised in a benzocaine solution, blood samples were withdrawn into syringes containing a drop of 10% EDTA for hematological analysis. The results were compared between fish farms and seasons, which are well delimited in southern Brazil. In a traditional fish farm in Joinville in the summer, there was an increase in the percentage of hematocrit and in the red blood cell count. The highest values of total leukocytes were found in fish from fee-fishing in Blumenau in the autumn while the lowest values occurred in those from swine consorted system in Ituporanga in the summer. Thrombocytosis was observed in the autumn, and lymphocytosis was found in both the autumn and winter in tilapia from all fish farms investigated. Neutrophilia was only observed in winter and autumn in fish from Blumenau and Ituporanga. This work demonstrated the influence of seasonality and the handling characteristics of each fish farm on certain hematological parameters in Nile tilapia. Neste presente estudo avaliou-se a influência da sazonalidade sobre os parâmetros hematológicos de tilápia-do-nilo cultivada no estado de Santa Catarina, Sul do Brasil. Um total de 240 peixes foi examinado durante as quatro estações do ano, entre abril de 2007 e março de 2008 em pisciculturas de três diferentes sistemas de cultivo. Após anestesia com benzocaína, amostras de sangue foram coletadas com seringas contendo EDTA 10% para análise hematológica. Os resultados foram comparados entre as pisciculturas e as estações, as quais são bem definidas no Sul do Brasil. Nos peixes de piscicultura tradicional em Joinville, no verão, houve aumento no hematócrito e do número de eritrócitos. Os maiores valores de leucócitos totais foram observados no outono nos animais de pesque-pague em Blumenau, enquanto os menores valores nos animais oriundos de piscicultura consorciada com suínos em Ituporanga no verão. Trombocitose foi observada no outono, e linfocitose ocorreu tanto no outono quanto no inverno em tilápia de todas as propriedades analisadas. Neutrofilia apenas foi observada no inverno e outono nos peixes de Blumenau e Ituporanga. Este estudo demonstrou a influência da sazonalidade e das características de manejo de cada piscicultura sobre os parâmetros hematológicos de tilápia-do-nilo.

This study evaluated seasonality in hematological parameters of Nile tilapia cultured in the state of Santa Catarina, southern Brazil. A total of 240 fish were examined during four seasons between April 2007 and March 2008 in three different fish farms. After being anesthetised in a benzocaine solution, blood samples were withdrawn into syringes containing a drop of 10% EDTA for hematological analysis. The results were compared between fish farms and seasons, which are well delimited in southern Brazil. In a traditional fish farm in Joinville in the summer, there was an increase in the percentage of hematocrit and in the red blood cell count. The highest values of total leukocytes were found in fish from fee-fishing in Blumenau in the autumn while the lowest values occurred in those from swine consorted system in Ituporanga in the summer. Thrombocytosis was observed in the autumn, and lymphocytosis was found in both the autumn and winter in tilapia from all fish farms investigated. Neutrophilia was only observed in winter and autumn in fish from Blumenau and Ituporanga. This work demonstrated the influence of seasonality and the handling characteristics of each fish farm on certain hematological parameters in Nile tilapia.