Antonio Glaydson Lima Moreira

Performance of Carassius auratus with different food strategies in water recirculation system

The efficiency of a recirculation system for the cultivation of C. auratus, fed with natural and artificial diets was evaluated. The experiment consisted of four treatments with four replicates. The first two treatments used recirculation system and the last two static system. In the first and fourth treatment, animals were fed with brine shrimp biomass (50% CP), while in the second and third treatments a commercial flake ration (42% CP) was used. At the end of cultivation (60 days), water samples were taken from all experimental units and subjected to standard plate count for determining the density of mesophilic bacteria. Final weight (g), final length (cm), specific growth rate (% day -1 ) and weight gain (%) were significantly different (p<0.05) among tested diets, but the culture systems did not affect fish performance. There was significant difference (p<0.05) between systems for total ammonia and nitrite. Animals fed with brine shrimp biomass acquired more intense and brighter colors than those fed only with commercial flake food. The values of standard plate count of mesophilic bacteria ranged from 7.0 × 10 3 to 1.1 × 10 4 CFU.ml -1 . In this study we observed that C. auratus is a species tolerant to adverse water conditions, perhaps with increased stock densities, the recirculation system could play some positive role on the zootechnical performance of cultured animals.

Efeito do eugenol como agente mitigador do estresse no transporte de juvenis de tilápia do Nilo

Brazil stands out in the American scene as one of the countries with the greatest potential for fish farming mainly in fresh water. Nile tilapia (Oreochromis niloticus) stands out being the most cultivated fish species in our country. Methodologies to reduce the interference of stressors agents in vital and physiological functions of fishes are important during handling. This study aimed to evaluate the effect of eugenol in the metabolic and ionic responses of juvenile Nile tilapia, submitted to transport in plastic bags, at different densities in order to verify the efficiency of the product as an mitigate agent of stress. Eugenol was used at a concentration of 15mg L-1 in water. The evaluated densities were 4, 7 and 10 fish L-1, which were equivalent to 140, 245 and 350g L-1. After four hours of transport the metabolic (glucose and lactate) and ions parameters (chloride, magnesium and calcium) were evaluated, as well as the water quality in the plastic bags. For the two metabolic parameters, the use of the eugenol in order to reduce the stress response was not satisfactory. There was an increase in blood glucose level at the densities of 140 and 350g L-1 immediately after termination of the transport, and the level of fish lactate content at the density of 245g L-1 had increased after 24 hours indicating that the animals could not maintain the initial homeostasis. Among the concentrations of the evaluated ions magnesium suffered the greater variation. We can conclude that the addition of 15 mg L-1 of eugenol in the water during the transport of juvenile Nile tilapia at densities of 140, 245 and 350g L-1 was not able to minimize stress responses.