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Stocking density and water salinity on pacamã larvicultureAbstract -The objective of this work was to evaluate the effect of stocking density and water salinity levels on Lophiosilurus alexandri (pacamã) larvae rearing fed with Artemia sp. nauplii. Three stocking densities were used: 20, 40 and 60 larvae L -1 (D 20 , D 40 and D 60 , respectively). For each density, three different levels of salinity were tested: freshwater (S 0 ), 2‰ (S 2 ) and 4‰ (S 4 ), in a completely randomized design, in a 3x3 factorial scheme, with three replications. The growth, survival, mortality, cannibalism, production and nonionized ammonia levels were evaluated. The nonionized ammonia levels were higher at D 40 and D 60 . At 10 days of feeding, the weight was affected negatively in D 40 and D 60 associated to higher water salinity (S 4 ). The higher survival was verified in D 20 S 2 treatment, while smaller values were found in S 4 , regardless of the density used. Small mortality rate and no cannibalism were observed. The juvenile final production was also influenced by the evaluated variables. Larvae of L. alexandri can be reared, during the first ten days of exogenous feeding, in freshwater or slightly saline water (2‰) with higher juvenile production at density D 60 .

RESUMO -O experimento foi conduzido com o objetivo de desenvolver técnicas de manejo durante a larvicultura de trairão, realizando cultivos em água doce ou ligeiramente salinizada, utilizando náuplios de Artemia como alimento vivo. No início da alimentação exógena, oito dias após a eclosão, as larvas foram contadas e estocadas em 12 recipientes com volume útil de 1,5 L cada, dotados de sistema de aeração, numa densidade de 10 larvas/L, distribuídos dentro de três tanques de 130 L, contendo água com temperatura controlada (29,5°C). Os tanques foram totalmente cobertos com lona plástica preta, mantendo o ambiente interno escuro, e descobertos somente para os manejos diários. As larvas foram submetidas a três tratamentos: cultivo em água doce; em água a 2‰ de salinidade; e em água a 4‰ de salinidade. Cada tratamento teve quatro repetições. A alimentação foi fornecida nas proporções diárias de 300 náuplios de Artemia/ larva, do primeiro ao quinto dia, de 600 náuplios de Artemia/larva, do sexto ao décimo dia e de 900 náuplios de Artemia/larva, do décimo primeiro ao décimo quinto dia, divididos em três refeições. Ao final do experimento, foram avaliadas a sobrevivência, o crescimento (comprimento e peso), a taxa de crescimento específico e a taxa de resistência ao estresse. Após 15 dias de tratamento, não foram verificadas diferenças significativas entre os resultados das variáveis analisadas. As condições de cultivo mostraram-se eficientes, possibilitando altas taxas de sobrevivência (valores médios superiores a 91,6%), sendo a Artemia um alimento atrativo. Os níveis de salinidade utilizados não afetaram o desenvolvimento das larvas e alevinos.Palavras-chave: trairão, Hoplias lacerdae, larvicultura, salinidade, canibalismo, Artemia Trairao (Hoplias lacerdae) Larviculture in Slightly Saline FreshwaterABSTRACT -The objective of this work was the development of larviculture handling technics to rear trairao in slightly saline freshwater, with Artemia nauplii as live food. At the beginning of exogenous feeding, eight days after hatching, trairao larvae were counted and stocked in twelve 1.5-L vessels, equipped with aeration, at 10 larvae/L density. The vessels were distributed in three 130-L tanks filled with controlled temperature water (29.5°C). The tanks were covered with black plastic to keep the environment dark, and uncovered only for daily management. The larvae were submitted to three treatments with four replicates, as follows: freshwater culture; water with 2‰ salinity; and water with 4‰ salinity. For the first five days, larvae were fed 300 Artemia nauplii/larvae. In the subsequent five days, larvae were fed 600 Artemia nauplii/larvae, and from the 11 th to the 15 th day, 900 Artemia nauplii/larvae, divided in three portions. At the end of the experiment, survival, growth (length and weight), specific growth rates and stress resistence rate were evaluated. At the end of 15 days of culture, no significant differences were observed among analyzed results of the different treatments. Rearing conditions were effic...

The effects of different water flow rates and feed training on the production of "pacamã" Lophiosilurus alexandri juveniles were evaluated. In the first experiment, nine day post-hatch larvae (n= 2,400) were stocked at a density of 5 larvae/L. Different water flow (F) rates were tested: F 1 = 180; F 2 = 600; F 3 = 1,300; and F 4 = 2,600mL/min. Artemia nauplii were offered as food during the first 15 days of active feeding. In the second experiment for feed training, 720 juveniles (total length of 22.2mm) were stocked at a density of 1.5 juveniles/L. A water flow rate similar to F 1 was used. The use of extruded dry diet was tested, and feed training was done with and without other enhanced flavors (Artemia nauplii or Scott emulsion). The water flow rates did not influence the survival or growth of L. alexandri. Cannibalism occurred during feed training. The worst survival, specific growth rate and high mortality were found with the use of extruded dry diet, while similar values were registered with the different feed training diets used. Reduced water flow rate can be used to lower water consumption during larviculture and feed training of L. alexandri.Keywords: feed training, juvenile production, larviculture, Lophiosilurus alexandri, water flow RESUMO Avaliaram-se os efeitos de diferentes fluxos de água e do condicionamento alimentar sobre a produção de juvenis de pacamã Lophiosilurus alexandri. Larvas com nove dias pós-eclosão (n=2.400) foram estocadas na densidade de 5 larvas/L. Diferentes fluxos (F) de água foram testados

The aim of this study was to evaluate the growth and survival of pacu, Piaractus mesopotamicus, larvae reared in different salinities and to determine the Artemia nauplii life span in freshwater and in saline water. First feeding 5‐d‐old pacu larvae were reared in freshwater or at 2, 4, 6, 8, 10, 12, and 14 ppt salinities. The larvae were reared in 1.5‐L aquaria at a density of 10 larvae/L with three replicates per treatment. After 10 d of rearing, significant differences (P < 0.05) were observed for growth and survival. Larval growth was higher at 2 and 4 ppt, and survival at 2 ppt was 100%. In freshwater and at 4, 6 and 8 ppt, the survival was 91.1, 93.3, 73.3, and 39.9%, respectively. At higher salinities, there was 100% mortality after 2 h (12 and 14 ppt) and 8 h (10 ppt) of exposure. The slightly saline water of at least 2 ppt increased the Artemia nauplii life span compared to the life span in freshwater. Later, in a second trial, 5‐d‐old pacu larvae were reared in freshwater and at 2 and 4 ppt salinities during the first 5 or 10 d of active feeding, and then the fish were transferred to freshwater. At the end of 15 d, larval growth was lower in freshwater (42 mg) than in treatments 2 and 4 ppt (59–63 mg). The abrupt transfer of fish from freshwater to slightly saline water and the return to freshwater did not affect the survival rates (89–97%). The larvae were able to adapt to these saline environments and handle abrupt changes in salt concentration. We concluded that salinity concentration of 2 ppt can be used for pacu larval rearing, allowing the Artemia nauplii lifetime to last longer and cause faster fish growth.

RESUMO -Este experimento foi conduzido com o objetivo de avaliar o condicionamento alimentar de alevinos de trairão (Hoplias cf. lacerdae). Foram utilizados seis aquários com capacidade para 20 litros cada, dotados de sistema artificial de aeração, temperatura controlada (27±0,5 o C), cobertos com lona plástica preta, mantendo o ambiente interno escuro todo o tempo (0L:24E), sendo descobertos apenas para os manejos diários. Alevinos de 2,9±0,2 cm de comprimento foram estocados a uma densidade de 4 animais/L e submetidos aos seguintes tratamentos: aceitação direta de dietas artificiais e condicionamento alimentar por meio da substituição da ração semi-úmida por ração seca. Ao final do experimento, foram obtidas taxas médias de sobrevivência de 27,50 e 96,66% para o primeiro tratamento e segundo tratamentos, respectivamente, evidenciando que o condicionamento alimentar é um manejo eficiente na produção e sobrevivência de alevinos de trairão.Palavras-chave: condicionamento alimentar, dietas artificiais, Hoplias cf. lacerdae, trairão Training Strategies Trairao Fingerlings (Hoplias cf. lacerdae)ABSTRACT -An evaluation of training strategies in fingerlings of trairao was carried out. The experimental design included six 20 L tanks with artificial aeration, controlled temperature variation (27±0.5°C), and continuously darkened (0L:24D), except during daily management. Fingerlings with 2.9±0.2 cm long were kept at a 4 specimens/L and they were allotted to the following treatments: the first was direct offering of artificial diet and the second involved training strategies by means of the replacement of semi humid food for dry food. At the end of the experiment, average survival rates were 27.5 and 96.66% for the first and second treatments, respectively, demonstrating that feeding conditioning is an efficient management in production and survival of Hoplias cf. lacerdae fingerlings. . Zootec., v.31, n.5, p.1881-1885, 2002 Introdução O trairão (Hoplias cf. lacerdae), espécie carnívora, apresenta carne de excelente qualidade, podendo ser comparada com a de muitos peixes nobres brasileiros, tendo grande aceitação por parte da população; além disso, apresenta características desejáveis para a pesca esportiva, devido a sua agressividade. Estas caracterís-ticas evidenciam o grande potencial desta espécie para a piscicultura nacional. Entretanto, muitos obstáculos vêm sendo encontrados em relação à criação em larga escala dessa espécie para atender a demanda do mercado consumidor, como dificuldade na aquisição de matrizes de qualidade e no manejo alimentar tanto dos adultos quanto dos alevinos; altos custos de manutenção de reprodutores; falta de estruturas e tecnologia adequada; e pouco conhecimento da biologia dessa espécie. R. BrasPara solucionar parte desses obstáculos, visando o desenvolvimento de criação de espécies carnívoras dentro do cenário da aqüicultura nacional, vários pesquisadores e empresas têm investido esforços na busca de tecnologia para a produção intensiva desses peixes (Campos, 1998;Machado et al., 1998...

RESUMO -O experimento foi realizado com o objetivo de se desenvolver estratégias de manejo alimentar durante a larvicultura de trairão. Larvas com oito dias de vida foram contadas individualmente e alojadas na densidade de 30 larvas/L em 20 unidades experimentais com volume útil de 5 L cada. As larvas foram submetidas a quatro tratamentos de freqüência alimentar: F1 -uma vez ao dia; F2 -duas vezes ao dia; F3 -três vezes ao dia; F4 -quatro vezes ao dia, cada um com cinco repetições. A alimentação foi fornecida na mesma quantidade em todos os tratamentos. Para avaliação do crescimento dos animais, foram realizadas biometrias a cada cinco dias. Após 15 dias sob os tratamentos, quando os animais estavam com 23 dias de vida, o experimento foi encerrado, avaliando-se também as taxas de sobrevivência, de mortalidade, de canibalismo e de resistência ao estresse. Na primeira avaliação biométrica, aos 13 dias de vida, não foram encontradas diferenças significativas no crescimento das larvas submetidas às diferentes freqüências alimentares. No entanto, aos 18 e 23 dias de vida, os animais do tratamento F1 apresentaram as menores médias de comprimento e peso. Não foi encontrado efeito significativo da freqüência alimentar sobre as taxas de crescimento específico durante a larvicultura. As diferentes freqüências de alimentação impostas não influenciaram as taxas de sobrevivência, de mortalidade, de canibalismo e de resistência ao estresse, destacando-se as elevadas taxas de sobrevivência (acima de 93%) obtidas durante o período de larvicultura. Portanto, pelo menos durante a criação inicial (até 23 dias de vida), as larvas de trairão podem receber manejo mais simplificado, com fornecimento de alimento apenas duas vezes ao dia, sem prejuízo ao desenvolvimento e à produção de animais.Palavras chave: freqüência de alimentação, Hoplias lacerdae, larvicultura, trairão Effects of Feeding Frequency on Larval Rearing of Trairao (Hoplias lacerdae)ABSTRACT -The effects of feeding management strategies on larval rearing of trairao were evaluated in this trial. Eight-d old larvae were counted and stocked in 20 experimental containers (units with volume of 5 L each), with constant aeration and temperature. The stocking density was 30 larvae/L. The following treatments (feeding frequency) were used: F1 -once a day, F2 -twice a day, F3 -three times a day, F4 -four times a day, each with five replicates. Feeding rate was equal for all treatments. In order to evaluate the animal growth, some samples were collected every five days. At the end of the experiment, after 23 days, the survival, mortality, rates of cannibalism and stress resistance were also evaluated. No significant difference was observed among the growth parameters at 13 days. However, after 18 and 23 days, F1 treatment showed the lowest length and weight averages. No differences of larval specific growth rate due to the feeding frequencies were observed. No effects of feeding frequency on rates of survival, mortality, cannibalism and stress resistance were detected. The surviva...