ResumoOs ácidos algínicos são extraídos de algas marinhas e quando utilizados na dieta dos peixes podem induzir respostas imunomoduladoras e imunoestimulantes. AbstractThe alginic acid is extracted from seaweed and when used in fish ration may induce immunomodulatory and immunostimulants responses. This study aimed to evaluate the effect of alginic acid incorporated in the ration on performance and handling of juvenile Nile tilapia, Oreochromis niloticus. The first phase of the experiment occurred in two excavated ponds earth. 57,000 juveniles were used for Nile tilapia, local strains with the average weight of 14 grams. The juvenile Nile tilapia received the experimental diet treated with ergosan at a dose of 1% of the diet. The survival rate of fish and feed conversion in the experimental Nile tilapia was higher than the control Nile tilapia. In the second stage 54,126 juveniles with average weight 40.63 grams, were used. These fish were transferred to 16 fish cages. There were no significant differences in mortality rate between treatments. The highest mortality occurred between the third and seventh days after the handling. The data confirm that the transfer of juvenile Nile tilapia in the ponds to fish cages is a strong stressor.

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