Tilapia larviculture in freshwater and in slightly saline water

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.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

Anesthetic effect of eugenol in juvenile pacamã

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%.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%

Effect of water temperature and prey concentrations on initial development of Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae), a freshwater fish

The aim of this study was to investigate the effects of water temperature and prey concentrations (Artemia nauplii) on the initial development of Lophiosilurus alexandri larvae. The experiment was conducted using a 4 x 2 factorial design, with four water temperatures (23, 26, 29 and 32 °C), two different initial prey concentrations (P700 and P1,300) and three replicates. Feeding was increased during the fifteen-day experiment. At the end of the experiment, the survival and condition factor were affected only by prey concentrations, with elevated numbers of Artemia nauplii leading to higher averages of these variables. The total length (TL) and specific growth rate were separately influenced by temperature and prey concentration, without interaction between them, and weight showed an interaction with these factors. In general, an increase of temperature (23 to 32 °C) improved the growth and nitrogen gain in L alexandri larvae. For TL, the optimal temperatures estimated were 31.4 and 31.0 °C for P700 and P1,300, respectively. Similar mean body weight larvae and nitrogen gain were observed at 23 °C for both levels of prey concentrations. For other temperatures, the P1,300 level provided greater weight gain for L. alexandri. Therefore, it is suggested that temperatures between 29-32 °C combined with a higher level of prey concentration maximise the development and nitrogen gain in L. alexandri larvae. Moreover, this is the first result about nitrogen incorporation in neotropical fish larvae

Efeito anestésico do eugenol em juvenis de pacamã

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%

Incubação de ovos de pacamã com florfenicol

O objetivo deste trabalho foi avaliar o efeito de doses de florfenicol na incubação de ovos de pacamã (Lophiosilurus alexandri). Na primeira etapa, os ovos foram submetidos a concentrações de florfenicol entre 0 e 500 mg L-1, durante 24 horas. Na segunda etapa, as larvas foram observadas até o sétimo dia após a eclosão. Na terceira etapa, as larvas foram alimentadas por dez dias. Peso e comprimento apresentaram respostas que variaram de acordo com a fase de desenvolvimento e as concentrações de florfenicol. Concentrações menores que 309 mg L-1 de florfenicol podem ser usadas sem afetar as larvas nas fases posteriores

Performance and stress resistance of Nile tilapias fed different crude protein levels

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

Stocking density in the larviculture of Nile tilapia in saline water

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