ABSTRACT
The aim of this study was to evaluate three stocking densities (20, 40 and 60 larvae L-1), and two daily prey concentrations (400 and 700 Artemia nauplii larvae-1) during the first seven days of active feeding (first phase). In the second phase was evaluate the effect of the different feeding regimes: fasting, dry diet (55% crude protein), Artemia sp. and mixed feeding (Artemia sp. plus dry diet), after 17 days of active feeding on Rhinelepis aspera larviculture. In the first phase, growth was affected only by prey concentration. In the second phase, the dry diet induced higher growth rates than fasting, but lower growth rates than the other treatments. The acceptance of the dry diet was evidenced by an increase in the growth rate from 4.6% day-1 in the first five days to 10.7% day-1 in the following five days of feeding. Survival was similar among dry diet, mixed feeding and Artemia nauplii treatments. R. aspera larvae can be reared during the first seven days of active feeding at a density of 60 larvae L-1, after which they can be fed with a commercial dry diet.
ABSTRACT
The aim of this study was to analyze the salinity tolerance of pacamã Lophiosilurus alexandri larvae at different ages. The test was conducted in post-hatching-larvae and larvae with 8 and 12 days old post-hatching. Larvae were acclimatized to experimental conditions for 24h, kept in 18 plastic tanks with 1 L at a density of 15 larvae L-1. After this period, larvae were subjected to the salinities: freshwater, 2, 4, 6, 8 and 10 g salt L-1, and observed over a period of 96h. Post-hatching larvae exhibited complete mortality in 6, 8 and 10 g salt L-1. Survival was 100% in freshwater, 2 and 4 g salt L-1 although with the decrease in weight and length values to the salinities of 2 and 4 g salt L-1. The CL(I)50-96h of larvae 8 days old post-hatching was 8.9 g salt L-1. The weight was diminished with the increase in salinity, but no difference was registered in length between the different treatments. Larvae 12 days old post-hatching did not show differences in length and weight. The survival was lower in 8 and 10 g of salt L-1. Larvae 8 and 12 days old post-hatching changed their swimming activity behavior to saline water up to 6 g of salt L-1. Pacamã larvae showed higher tolerance to the different salinities with larval development.
O objetivo deste trabalho foi avaliar a tolerância de larvas de pacamã Lophiosilurus alexandri ao teste agudo de salinidade da água em diferentes idades. Os testes foram realizados em larvas recém-eclodidas, com oito e 12 dias pós-eclosão. As larvas foram aclimatadas às condições experimentais por 24h, sendo estocadas em 18 tanques plásticos de 1 L na densidade de 15 larvas L-1. Após esse período, as larvas foram transferidas para as salinidades: água doce, 2, 4, 6, 8 e 10 g de sal L-1 e observadas durante 96h. Larvas recém- eclodidas apresentaram mortalidade total em 6, 8 e 10 g de sal L-1 e 100% de sobrevivência para água doce, 2 e 4 g de sal L-1; porém, com redução dos valores de peso e comprimento mediante as duas salinidades. Larvas com oito dias pós-eclosão apresentaram CL(I)50-96hde 8,9 g de sal L-1. Para o peso, verificou-se redução gradativa a partir da salinidade de 2 g de sal L-1, mas sem diferenças para o comprimento das larvas entre os tratamentos. Para as larvas com 12 dias pós-eclosão, não se registraram diferenças no comprimento e peso e a sobrevivência foi menor a 8 e 10 g de sal L-1. Larvas com oito e 12 dias pós-eclosão tiveram alterações no comportamento natatório em salinidades superiores a 6 g de sal L-1. Larvas de pacamã apresentaram maior tolerância às diferentes salinidades da água com o desenvolvimento ontogenético.
ABSTRACT
Sixty-six trairão (Hoplias lacerdae) fingerlings (average weight of 2.0±0.5 g and total length of 5.8±0.2 cm), trained to accept dry rations, were allotted to six 15-L aquariums, with aeration and controlled temperature (24.0±0.5ºC), in a density of 0.7 juveniles/L, aiming to evaluate the effects of darkness on fish productive performance. The treatments consisted of two photoperiods: 12 hours light: 12 hours dark (12L:12D) and 0 hour light: 24 hours dark (0L:24D), with three replicates. Fingerlings were fed ad libitum a commercial extruded diet (42% CP), twice a day. The aquariums were cleaned daily for excrement withdrawal through siphoning, exchanging » total volume. At the end of the experiment (30 days), weight gain, feed:gain ratio and survival and cannibalism rates were evaluated. The results showed that darkness did not affect the productive performance of trairão juveniles
Sessenta e seis alevinos de trairão (Hoplias lacerdae) (peso médio de 2,0±0,5 g e comprimento total de 5,8±0,2 cm) condicionados à aceitação de rações secas foram distribuídos em 6 aquários de 15 L de água com temperatura de 24,0±0,5ºC, densidade de estocagem de 0,7 juvenis/L e aeração constante, com o objetivo de avaliar a ausência de luz no desempenho produtivo dos peixes. Os tratamentos consistiram dos fotoperíodos: 12 horas luz:12 horas escuro (12L:12E) e 0 horas luz:24 horas escuro (0L:24E), com 3 repetições cada. Os alevinos foram alimentados duas vezes ao dia, com ração comercial extrusada (42% proteína bruta). Diariamente, os aquários foram sifonados com a troca de 25% do volume total de água. Ao final de 30 dias, foram avaliados ganho de peso, conversão alimentar e taxas de sobrevivência e de canibalismo. Os resultados demonstraram que a ausência de luz não influenciou o desempenho produtivo dos alevinos de trairão
ABSTRACT
This experiment was carried out to evaluate the effects of the stocking density on trairao larvae rearing. Seven days old larvae were submitted to four different stocking densities: 10, 30, 60 and 90 larvae/L. Sixteen vessels with 5 L each supplied with constant aeration were kept in a thermostatic bath. Each treatment had four replications. In order to keep the internal environment dark, all the experimental units were covered with a black plastic and it was uncovered only during the daily management. At the end of the experiment, after 15 days of feeding with Artemia nauplii, no significant differences were found (P > 0.05) on growth among the evaluated densities. The same results were also registered for the survival, mortality and cannibalism rates. Higher stocking density resulted in higher production of trairao larvae rearing, allowing intensive rearing of this species in this phase
O objetivo do experimento foi avaliar o efeito da densidade de estocagem na larvicultura do trairão. Larvas com sete dias de vida foram submetidas a quatro densidades de estocagem: 10, 30, 60 e 90 larvas/L. Foram utilizados 16 recipientes com volume útil de 5 L cada, dotados de aeração constante e dispostos em sistema de banho termostatizado. Cada tratamento teve quatro repetições. As unidades experimentais foram cobertas com lona plástica preta para manter o ambiente interno escuro, sendo descobertas somente para o manejo diário. Ao final do experimento, após 15 dias de alimentação com náuplios de Artemia, não foram encontradas diferenças significativas (P > 0,05) de crescimento dos animais nas diferentes densidades. Esse mesmo resultado também foi observado com relação às taxas de sobrevivência, de mortalidade e de canibalismo. A utilização da maior densidade de estocagem resultou em maior produção de larvas de trairão, possibilitando a criação mais intensiva da espécie nessa fase