From early development until the completion of metamorphosis, fat snook (Centropomus parallelus) larvae are commonly fed the rotifers Brachionus spp. and Artemia spp. nauplii. In this study, cultivated copepods Acartia tonsa were evaluated as feed for 15-to 45-day-old larvae. Two experiments were performed using twelve 30-L tanks stocked with 3.3 fat snook larvae L-1. Their initial mean weight and length were 1.35 ± 0.01 mg (mean ± standard deviation) and 3.83 ± 0.33 mm for 15-day-old larvae and 2.79 ± 1.2 mg and 6.99 ± 0.88 mm for 31 -day-old larvae. Three dietary treatments were carried out in four replicates, including Rotifer (R), Artemia (A) and/or Copepod (C). Experiment 1 included Diet RA (control), Diet RC and Diet RCA; while experiment 2 included Diet A (control), Diet C and Diet AC. The survival and growth of larvae fed the Diet RCA in experiment 1 were significantly higher than the others. In experiment 2, the inclusion of copepods in the diet did not improve survival and growth, however, larvae fed Diet C had the highest DHA/EPA ratio. We conclude that the copepod Acartia tonsa provides an important nutritional benefit to fat snook larvae undergoing metamorphosis.

This research represents the first result of studies of the common snook Centropomus undecimalis larvae from broodstock matured in captivity in Brazil. The aim of this study was to evaluate if the inclusion of Acartia tonsa nauplii improves stress resistance of common snook larvae. The larvae were fed with: rotifers Brachionus plicatilis (10 to 15 mL-1); A. tonsa nauplii (0.25 to 0.5 mL-1) and rotifers (5 to 7.5 mL-1), and A. tonsa nauplii (0.12 to 0.25 mL-1). The average percentage of survival of the treatments was 11.9%. At 20 days of age, larvae were subjected to thermal stress. Subsequently, the stress resistance was evaluated. Common snook larvae fed B. plicatilis+A. tonsa reached a higher weight and length (7.5 ± 0.00 mg and 9.1 ± 0.23 mm, respectively) and resisted more heat stress (87.4%) than larvae fed other foods, indicating that the feed mixture is satisfactory as a starter diet for larvae of common snook. However, more research is needed to confirm these results.

Esta investigación constituye el primer resultado de los estudios de larvas de róbalo blanco Centropomus undecimalis a partir de reproductores maduros mantenidos en cautiverio en Brasil. El objetivo de este estudio fue evaluar si la inclusión de nauplios de Acartia tonsa mejora la resistencia al estrés de las larvas de róbalo blanco. Las larvas se alimentaron con rotíferos Brachionus plicatilis (10 a 15 mL-1); nauplios de A. tonsa (0,25 a 0,5 mL-1) y rotíferos (5 a 7,5 mL-1), y nauplios de A. tonsa (0,12 a 0,25 mL-1). El promedio de supervivencia de los tratamientos fue 11,9%. A los 20 días de edad, las larvas fueron sometidas a estrés térmico. Posteriormente, se evaluó la resistencia al estrés. Las larvas de róbalo blanco alimentadas con B. plicatilis+A. tonsa alcanzaron un mayor peso y longitud (7,5 ± 0,00 mg y 9,1 ± 0,23 mm, respectivamente) y resistieron más al estrés por calor (87,4%) que las larvas alimentadas con los demás alimentos, lo que indica que la mezcla de alimentación es satisfactoria como una dieta inicial para larvas de róbalo blanco. Sin embargo, se necesita más investigación para confirmar estos resultados.

O controle do sexo dos peixes é uma técnica promissora na aquicultura, pois permite obter vantagens associadas a um dos sexos. Sendo assim, o objetivo deste trabalho foi avaliar o efeito do hormônio 17β-estradiol (E2) na feminização, crescimento e sobrevivência de juvenis de robalo-flecha (Centropomus undecimalis). Durante 45 dias, os juvenis foram submetidos a três dietas (controle, 50, 100 mg E2 kg-1 de ração) com três repetições cada. Após este período, os peixes passaram a ser alimentados somente com ração comercial sem adição de hormônio. Durante o período de administração do E2, os peixes do controle cresceram mais que os dos outros tratamentos. No final do experimento, no tratamento com 50 mg E2 kg-1, 26% dos peixes eram machos, 68.42% eram fêmeas e 5.26% eram intersexo. No tratamento com 100 mg E2 kg-1, 10% dos peixes eram machos e 90% eram fêmeas. Após 11 meses não houve diferença de crescimento entre os tratamentos. Este trabalho mostrou que é possível obter 90% de fêmeas de robaloflecha utilizando rações com 100 mg E2 kg-1 durante 45 dias sem danos ao crescimento ou à sobrevivência.

Sex control in fish is a promising technique for aquaculture, since it gives advantages associated with one sex. The aim of this study was to investigate the feminization of common snook (Centropomus undecimalis) by oral administration of two doses of estradiol-17β (50 and 100 mg E2 kg-1 feed) and control treatment for 45 days and to evaluate their effects on the sex ratio, growth and survival of common snook juveniles. After this period, fish were fed only with commercial feed without hormone supplementation. During the period of E2 administration, the control fish grew more than those in the other treatments. At the end of the experiment in the treatment with 50 mg E2 kg-1, 26.32% of the fish were male, 68.42% were female, and 5.26% were intersex. In the treatment with 100 mg E2 kg-1, 10% of the fish were male, and 90% were female. There was no difference in growth among the treatments after 11 months. This study showed that it is possible to obtain 90% common snook females using feeds with 100 mg E2 kg-1 for 45 days without impairing the fish growth or survival.

O desmame, ou seja, a substituição do alimento vivo por alimento inerte é uma etapa crítica para a produção de alevinos de peixes marinhos. Este trabalho teve por objetivo avaliar o efeito do período de co-alimentação (alimento vivo e inerte) sobre a sobrevivência, o crescimento e os custos de produção de juvenis do linguado Paralichthys orbignyanus. Durante o período de co-alimentação, os juvenis (idade inicial 32 dias) receberam Artemia enriquecida juntamente com ração. Foram testados três períodos de co-alimentação: 15, 20 e 25 dias, mais um grupo controle alimentado com Artemia enriquecida. Ao final do experimento (76 dias), os juvenis alimentados exclusivamente com Artemia enriquecida apresentaram sobrevivência (82%), peso (480±157mg) e comprimento (35,5±5,0mm) significativamente maiores (P<0,05) que os juvenis alimentados com ração. Não houve diferença significativa (P>0,05) no crescimento entre os juvenis alimentados com ração nos diferentes períodos, entretanto, um período maior de co-alimentação favoreceu a sobrevivência. Os resultados obtidos demonstram que os linguados alimentados exclusivamente com Artemia apresentam melhor performance do que aqueles alimentados com ração. Entretanto, o custo de produção quando a Artemia é substituída por ração aos 58 dias de vida é menor do que quando o desmame é realizado mais cedo ou quando os alevinos são alimentados apenas com Artemia.

Weaning is a critical period for production of marine fish juveniles. The objective of this research was to evaluate the effect of co-feeding on survival, growth, and cost of production after the weaning of juveniles of Brazilian flounder Paralichthys orbignyanus. Juvenile flounder (32 days after hatching) were fed on HUFA enriched Artemia and subsequently three periods of co-feeding with dry diets (15, 20, and 25 days) were tested, a control group, where flounder were fed exclusively on Artemia was also followed until the end of the experiment. Juveniles fed on Artemia showed significantly higher (P<0.05) survival (82%), weight (480±157mg) and total length (35.5±5.0mm) than flounder weaned into dry diets, independent of the co-feeding period. Growth was similar (P>0.05) for juveniles fed on dry diets, but a higher survival rate was registered when the co-feeding period was longer. The results obtained demonstrate that flounder fed exclusively on Artemia have a better performance than those weaned into dry diets. However, unitary cost of production is reduced when juveniles are weaned 58 days after hatching.