Influence of stocking densities in the nursery phase on the growth of Macrobrachium amazonicum reared in net pens

The Amazon river prawn (Macrobrachium amazonicum) is a native species with great potential for aquaculture, based on promising results obtained from experimental culture trials in Brazil. The influence of different stocking densities on the development of prawns reared in cages in the nursery phase as well as on their growth when transferred to grow-out net pens at lower densities was evaluated. In the nursery phase, juveniles I (0.157 +/- 0.014 g, 47 days old) were stocked in 0.5 m(-2) cages at densities of 400, 800 and 1200 m(-2). After 71 days, prawns were transferred to grow-out net pens of 2.0 m(-2), at a density of 20 juveniles II m(-2). The treatments were determined by the mean weights registered for the prawns (118 days old) previously stocked at 400, 800 and 1200 juveniles I m(-2) in the nursery phase: 0.94 +/- 0.07 g (T1), 0.61 +/- 0.04 g (T2) and 0.48 +/- 0.07 g (T3), respectively. In the nursery phase, mean survival was above 96%, whereas mean weights were significantly higher (P<0.05) for the density of 400 prawns m(-2). The highest biomass (276.7 g) and productivity (1152 juveniles II m(-2)) were registered at the density of 1200 prawns m(-2), differing significantly (P<0.05) from the lower densities. One month after the transfer of the animals to the net pens, there was recovery in the specific growth rate (SGR) of prawns in all treatments which was significantly higher (P<0.05) in T3 (4.01 +/- 0.36% day(-1)) and T2 (3.60 +/- 0.18% day(-1)). The feed conversion efficiency (FCE) in the first month after the transfer was also significantly higher (P<0.05) in T3 (78.2 +/- 19.1%) when compared to T1 (39.8 +/- 9.5%). These results suggest the occurrence of a compensatory growth in M. amazonicum after transferring them to lower densities, which can point out high densities for nursery cages as a viable practice. After 277 days of grow-out phase in net pens in the cold season, survival, mean weight and biomass did not differ significantly among the treatments, indicating the viability of using net pens in stocking prawns during autumn and winter, since the minimum temperature does not drop below 17 degrees C. Influence of stocking density during the nursery phase on the grow-out of prawns was not observed. The population structure in prawns reared in net-pens was similar to that observed in earthen ponds. (C) 2012 Elsevier B.V. All rights reserved.

Salt as a stress response mitigator of matrinxa, Brycon cephalus (Gunther), during transport

The present study evaluated the physiological responses of matrinxa, Brycon cephalus (Gunther), submitted to transport stress under the influence of sodium chloride, Different salt concentrations (0.0%, 0.1%, 0.3% and 0.6%) were added to four 200-L plastic tanks. Each tank was stocked with 30 fish (mean weight 1.0 +/- 0.2 kg) and transported for 4 h. Blood was sampled prior to transport and immediately after and 24 and 96 h after transport. Plasma cortisol and glucose and serum sodium and potassium, plasma chloride and ammonia were analysed, Changes in plasma cortisol were observed immediately after transportation, except in fish transported in 0.3% and 0.6% salt. Twenty-four hours later, this hormone had returned to its initial level in all fish. Blood glucose was not changed in fish treated with 0.6% salt immediately after transport, and returned to the initial level within 96 h after the other treatments. All treatments resulted in lower levels of plasma chloride after transport, except for fish treated with 0.6% salt, with fish treated with 0.0% and 0.3% salt recovering 24 h later, Serum sodium decreased immediately after transport only in the control fish, returning to the initial level 24 h later, the results indicate that treatment with 0.6% NaCl reduces most of the physiological responses of matrinxa to the stress of transport.

Transport stress in matrinxa, Brycon cephalus (Teleostei : Characidae), at different densities

Matrinxa, Brycon cephalus, is a native teleost fish from the Amazon Basin, and is of economic importance for cultivation for food and sport in Brazil. Mortality losses due to handling and transport of this stenohaline freshwater species are common. The effects of transportation at different densities on the biochemical stress responses of matrinxa (mean weight 1 kg) were examined. Fish were subjected to three different transport densities (100, 200, and 300 kg m(-3)) for four h in water with added salt (0.6%). The fish were bled at departure (baseline level), arrival (immediately after transportation) and at 24 and 96 h after arrival (recovery period). Blood glucose, cortisol, sodium, chloride, potassium and ammonia were used as stress bioindicators. No mortality was observed and no alterations in plasma cortisol were registered. However, blood glucose and ammonia levels increased and serum sodium and plasma chloride decreased on arrival for the fish transported at the highest densities. These stress responses were transient and the concentrations returned to baseline levels within 24 h. This study showed that matrinxa can be transported at densities as high as those tested in the present study, at least under the conditions employed in this study. A recovery period of at least 24 h is strongly recommended.

Desempenho produtivo de Pseudoplatystoma corruscans estocados em sistemas de criação: semi-intensivo (viveiro escavado) e intensivo (tanque-rede)

Objetivou-se comparar o desempenho produtivo e custos de produção de exemplares de pintado, Pseudoplatystoma corruscans, estocados em dois sistemas de criação: semi-intensivo (viveiro escavado, VE) e intensivo (tanque-rede, TR). Trezentos (300) peixes, com um ano de idade, foram estocados, sendo 150 em um VE (médias de peso e comprimento: 1,48±0,46kg e 57,31±6,42cm) e 150 divididos em três TR (médias de peso e comprimento: 1,27±0,34kg e 55,05±4,11cm). Foram alimentados com ração extrusada de 15mm (diâmetro) 40% PB e 3110kcal ED kg-1, ajustada mensalmente à quantidade de ração. Os parâmetros físico-químicos da água, observados durante o experimento, foram temperatura = 24,08°C±3,23; pH=6,89±0,39 e oxigênio dissolvido = 7,57±0,97mg L-1. Os reultados obtidos dos valores médios finais dos comprimentos (VE=74,07±4,34cm; TR=70,33±5,02cm) e pesos dos peixes (VE=3,41±0,58kg e TR=2,94±0,60kg) indicaram desempenho semelhante nos dois sistemas. As médias do fator de condição (0,09-0,036); ganho em peso diário (9,29g dia-1 - 8,95g dia-1); conversão alimentar (3,09-4,15); consumo total de ração (29,60g dia-1 - 74,16g dia-1); índice de crescimento (0,219-0,215) e sobrevivência (97,33-90,67%) para VE e TR, respectivamente. Houve interação significativa entre os sistemas de criação e mês (P<0,05). O quilo de peixe produzido foi de R$ 8,76 (US$ 2,85) e R$ 8,73 (US$ 2,33) para o VE e TR, respectivamente. Embora o VE tenha demonstrado melhor desenvolvimento durante o período e uma vantagem econômica, o índice de crescimento mostrou que ambos os sistemas tiveram desempenhos semelhantes.

Utilização de probiótico na dieta de reprodutoras de matrinxã (Brycon amazonicus)

This study aimed to analyze of using a probiotic (Bacillus subtilis) in the diet of breeding matrinxa (Brycon amazonicus) taking into account the number of oocytes, fertilization rate, hatching and final biomass. The experiment was carried out from March to November 2008. Fifty animals with mean weight 2.35 +/- 0.31 kg and mean length 53.00 +/- 1.96 cm. Two treatments were used T(1) = control group and T(2) = 10 g probiotic kg(-1) food. The induced breeding was carried out with crude extract of carp pituitary. The result showed that the number of oocytes released, fertilization rate and hatching rates were 5%, 34% and 36% higher than control group. The final total biomass of the control group was 3.6% higher compared to animals treated with probiotic. Concluded that is viable to include Bacillus subtilis in diet of matrinxa for optimizing reproductive indicators.

Population structure of pond-raised Macrobrachium amazonicum with different stocking and harvesting strategies

The effect of size-grading of juveniles prior to stocking, as well as selective harvesting, on the population structure of pond-raised Macrobrachium amazonicum was studied. A randomized-complete-blocks design with 4 treatments and 3 replicates was used. The treatments were: upper size-graded juveniles, lower size-graded juveniles, ungraded juveniles (traditional), and ungraded juveniles with selective harvesting. Twelve 0.01 ha earthen ponds were stocked at 40 juveniles m(-2), according to the relevant treatment. Every three weeks, random samples from each pond were obtained for biometry, and after 3.5 months, the ponds were drained and completely harvested. Animals were then counted, weighed, and sexed; males were sorted as Translucent Claw (TC), Cinnamon Claw (CC), Green Claw 1 (GC1), and Green Claw 2 (GC2), and females as Virgin (VF), Berried (BE), and Open (OF). The prawns developed rapidly in the ponds. attaining maturity and differentiating into male morphotypes after about 2 months in all treatments. The fast-growing juveniles (upper grading fraction) mostly did not constitute the dominant males (CC] and GC2) in the adult population. Population development was slower in ponds stocked with Lower prawns, whereas selective harvesting increased the frequency of GC1 and reduced the final mean weight of GC2 males. The proportion of males increased throughout the culture period, but was generally not affected by the stocking or harvesting strategies. Grading juveniles and selective harvesting slightly altered the population dynamics and structure, although the general population development showed similar patterns in ponds stocked with upper, lower, and ungraded juveniles, or selectively harvested. (C) 2010 Elsevier B.V. All rights reserved.

Efeito do manejo alimentar no desempenho do matrinxã Brycon amazonicus em tanques de cultivo

O objetivo deste estudo foi avaliar o efeito do horário, taxa e freqüência de alimentação no desempenho do matrinxã (Brycon amazonicus) em tanques de cultivo. O trabalho foi realizado no Centro de Aqüicultura da UNESP, Jaboticabal, SP, no período de outubro de 1997 a janeiro de 1998 sendo realizados três ensaios, em tanques de 200m² subdivididos em 4 de 50 m². No ensaio I foram medidos em 3 períodos (manhã-m; meio do dia-md e tarde-t) o consumo de ração, índice de ingestão, tempo de saciação e velocidade de ingestão em peixes com peso médio de 232,13 g, alimentados com ração extrusada (32% de PB). Não foi observada diferença significativa nos parâmetros analisados. No ensaio II, em peixes com peso médio de 233,98 g, foi medido o consumo médio de ração, em intervalos de duas horas, das 07 às 19 horas. O maior consumo ocorreu quando o matrinxã foi alimentado às 17 horas. No ensaio III, durante 57 dias, os peixes foram alimentados uma vez ao dia (m); uma vez ao dia (t); duas vezes ao dia(m/t) e três vezes ao dia (m,md,t). Peixes com peso médio inicial de 322,25 g receberam ração com 32% de PB, na quantidade de 2% do PV. Não foram observadas diferenças significativas no ganho de peso diário (3,17; 2,80; 3,04 e 2,81 g) e na conversão alimentar aparente (2,11; 2,48; 2,16 e 2,31:1). Concluiu-se que a freqüência de alimentação de uma vez ao dia, em qualquer horário, mostrou ser suficiente.

Length-weight relationship and condition factor of the mangrove crab Ucides cordatus (Linnaeus, 1763) (Crustacea, Brachyura, Ucididae)

A determinação da relação do peso úmido (WT) pela largura cefalotorácica (CW) do caranguejo U. cordatus e a análise da dinâmica temporo-sazonal do fator de condição foram realizadas com machos e fêmeas coletados mensalmente no período de 1998/2000, em Iguape (SP). A relação WT/CW foi determinada por análise de regressão, enquanto o fator de condição foi determinado individualmente para cada animal, bem como pela média mensal e sazonal para cada sexo. A relação WT/CW evidenciou um crescimento isométrico nos machos e alométrico negativo nas fêmeas, indicando que os machos atingem um peso corpóreo superior ao das fêmeas para um mesmo tamanho de referência. Tal fato está associado ao maior crescimento e peso dos quelípodos do macho. As médias do fator de condição das fêmeas foram maiores que as dos machos. Os menores valores do fator de condição ocorreram durante a primavera e verão, atingindo os maiores níveis durante o outono e inverno.

Influência de diferentes níveis de vitamina C na ração sobre parâmetros hematológicos de alevinos de Piaractus mesopotamicus Holmberg (Osteichthyes, Characidae)

Haematological changes in ascorbic acid deficient fishes, observed by some authors, awoked the interest in the haematological response of pacu, Piaractus mesopotamicus. The present work studied the influence of different levels of ascorbic acid (vitamin C) in the ration on the haematological parameters of pacu. Fishes at the beginning of the experiment, presented average body weight 8.64±1.62g and 6.15±0.33cm standard length, were fed with diets containing 0. 50, 100 and 200mg ascorbic acid/kg dry ration. The present work was developed for a period of 24 weeks at the Fish Nutrition Laboratory of Aquaculture Center of Universidade Estadual Paulista (Unesp), Jaboticabal (São Paulo). The fishes were distributed by the completely randomized design in 20 aquaria of 100 liters capacity with six animals in each and five fold treatment. Condutivity, alcalinity. pH and oxigen were measured weekly and temperature daily. The blood colect was done in 60 anesthetized fishes with 50mg MS-222/1. The results suggests that 50mg ascorbic acid/kg dry ration improved the mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and decreased haematocril in unsupplemented fishes, although not differing significantly (P>0.05). The erytrocyte diameter indicated the presence of macrocytic cells in unsupplemented fishes (P<0.05) and the regression analysis showed too reduced neutrophils in unsupplemenled ones, 50mg ascorbic acid/kg dry ration supplementation was enough to development and haematological responses. Furthtermore, the optimum level to the growth is 139mg vitamin C/kg dry ration (P<0.05).