Resumo -O objetivo deste trabalho foi avaliar o efeito de diferentes salinidades da água na larvicultura de tilápia. Larvas com cinco dias pós-eclosão foram estocadas em tanques de 6 L durante 30 dias. Os tratamentos experimentais foram água doce e água com 2, 4, e 6 g L -1 de sal, com seis repetições. As larvas mantidas a 6 g L -1 de sal apresentaram mortalidade total, antes de dez dias de alimentação ativa. Na salinidade a 4 g L -1 , a sobrevivência e o desempenho foram inferiores aos registrados para os animais mantidos em água doce e a 2 g L -1 de sal, com resultados semelhantes entre si.Termos para indexação: Oreochromis niloticus, desempenho, salinidade da água. Tilapia larviculture in freshwater and in slightly saline waterAbstract -The objective of this work was to evaluate the effects of different water salinities on tilapia larviculture. Larvae with five days post-hatching were stocked in tanks of 6 L each during 30 days. Treatments were carried out in freshwater and water at 2, 4, and 6 g L -1 salinity, with six replicates. Larvae kept at 6 g L -1 salinity showed total mortality before the ten days of active feeding. Survival and growth at 4 g L -1 salinity were lower than the ones registered for animals kept in freshwater and 2 g L -1 salinity, with similar results to one another.

This study evaluated the efficiency of the drainage system during the larviculture of Lophiosilurus alexandri. Moreover, we assessed the best feeding rate after feed training for juvenile production. The study was performed in three phases over 87 days. In phase 1 (40 days), larvae were fed live food and posteriorly submitted to feed training in two drainage systems: water drained on the surface (DS), and water drained into a tank column (DI). In the second phase (30 days), using only the DS system juveniles were fed a formulated diet at feeding rates, 2, 4, 6 and 8% of body wet weight. In the third phase (17 days), the fish from the second phase were fed until apparent satiation. At the first phase, the animals in the DS system exhibited greater survival rates and growth. The best feeding rate for daily weight gain, specific growth rate (SGR) and mean body weights were similar: 5.57, 5.13 and 5.68% respectively. In the third phase, an increased SGR was observed in the treatment groups that received lower feeding rates in the second phase (2 and 4%), which could indicate a possible compensatory growth rate.

-The objective of this study was to assess the possibility of increasing the stocking density in the larviculture of Nile tilapia, Oreochromis niloticus, in saline water. Six-day post-hatched larvae (average weight of 0.09±0.002 g), at the start of the exogenous feeding, were stocked in twelve 8 L tanks at densities of 1, 10, 20 and 30 larvae/L. The larvae were fed a diet consisting of 40% crude protein five times per day. During larviculture, water was kept at a salinity of 2 g of common salt/L. At the end of the 28-day experiment, the survival rate, length, weight, temperature, water salinity and conductivity were not affected by the different treatments. The dissolved oxygen and pH, however, decreased as density increased, whereas total ammonia concentration, turbidity and biomass showed a direct relationship with the increase of stocking density. Consequently, the present study shows for the first time that the larviculture of Nile tilapia is possible with up to 30 larvae/L in water with 2 g of salt/L.

-The objective of this study was to evaluate the effect of different levels of diet crude protein on the performance and stress resistance rate (Re) of Oreochromis niloticus larvae and fingerlings. In the first experiment, 5, 15 and 25 day-old animals were submitted to 1, 5, 7, 10, 15, 20, 30 and 40 minutes of air exposure on a sieve. In the second experiment, tilapia larvae were fed with 32, 40 and 55% crude protein (CP) diets. Animals after 15 and 30 days of feeding (21 and 36 days of life, respectively) were submitted to the air exposure test for 7 and 10 minutes. Re was estimated based on survival 24 hours after the tests. In the first experiment, it was observed that 5-day-old animals were more resistant than animals with 10 and 20 days of feeding (15 and 25 days of life, respectively), when Re starts to decrease for longer than 7 minutes. In the second experiment, the different diets affected survival, performance and Re, and, in general, the worst results observed were the ones for the animals which received the 55% CP diet. The air exposure tests were efficient to evaluate the effect of diet on the resistance rate of Nile tilapia.

Resumo -O objetivo deste trabalho foi avaliar o efeito do eugenol como anestésico para juvenis de pacamã (Lophiosilurus alexandri). Os animais foram divididos em dois grupos, denominados juvenil I (0,72 g) e juvenil II (7,44 g), e submetidos a seis tratamentos de eugenol (20, 40, 60, 80, 100 e 120 mg L -1 ), em dez repetições. Durante o experimento, foram realizadas biometrias e cronometragens dos tempos de indução e recuperação. Com o aumento das doses, o tempo de anestesia foi reduzido de 69 para 27 s, em juvenis I, e de 93,8 para 37,3 s em juvenis II. A sobrevivência foi de 100%.Termos para indexação: Lophiosilurus alexandri, anestesia, manejo, sobrevivência. Anesthetic effect of eugenol in juvenile pacamãAbstract -The objective of this work was to evaluate the effect of eugenol as an anesthetic in juvenile pacamã (Lophiosilurus alexandri). The animals were divided into two groups, named juvenile I (0.72 g) and juvenile II (7.44 g), and subjected to six treatments of eugenol (20, 40, 60, 80, 100, and 120 mg L -1 ) in ten replicates. During the experiment, biometrics and timing of induction and recovery times were measured. With the increasing doses, the anesthesia duration was shortened from 69 to 27 s in juvenile I and from 93.8 to 37.3 s in juvenile II. The survival rate was 100%.