Juvêncio Luís Osório Fernandes Pouey

Lethal concentration (CL50) of un-ionized ammonia for pejerrey larvae in acute exposure

Ammonia results from decomposition of effluents organic matter, e.g. feed wastes and fish faeces. Its un-ionized form can be toxic because diffuses easily through fish respiratory membranes, damaging gill epithelium and impairing gas exchanges. The objective of this work was determining the 96-hour CL50 of un-ionized ammonia for newly hatched pejerrey Odontesthes bonariensis larvae. Trials were set up completely randomized design, with three different concentration of un-ionized ammonia (0.57, 0.94, and 1.45 mg L-1 NH3-N) and a control treatment (n = 3). Experimental units were 20-L, aerated aquaria stocked with 20 larvae (average weight 3.9 mg). Pejerrey larvae exposed to un-ionized ammonia during 96 hours present 50% mortality at 0.71 mg L-1 NH3-N.

Suplementação de fitase microbiana na dieta de alevinos de jundiá: efeito sobre o desempenho produtivo e as características de carcaça

Este estudo foi realizado para avaliar os efeitos da adicao de diferentes niveis de fitase na dieta sobre o desempenho produtivo e as caracteristicas de carcaca de alevinos de jundia (Rhamdia quelen). Foram utilizados 208 alevinos com peso vivo inicial medio de 2,92±0,59g, distribuidos em um delineamento inteiramente casualizado com quatro tratamentos (0, 500, 1.000 e 1.500FTU kg-1) e quatro repeticoes. Na composicao das dietas, foram utilizados somente ingredientes de origem vegetal e o alimento foi fornecido duas vezes ao dia. A cada quinzena, foram avaliados os parâmetros produtivos e, ao termino do periodo experimental (45 dias), foram ainda realizadas avaliacoes nas carcacas. O ganho de peso medio foi significativamente crescente (P<0,05) entre os tratamentos sem adicao de fitase (0 FTU kg-1) e o nivel maximo utilizado (1500FTU kg-1) na dieta, variando de 1,24±0,27g para 1,73±0,23g, respectivamente. A taxa de crescimento especifico tambem teve efeito significativo (P<0,05) nos tratamentos sem fitase e 1.500FTUkg-1, passando de 0,78±0,12% para 1,07±0,11%. Entretanto, o extrato etereo na carcaca foi linearmente decrescente com os niveis de fitase na dieta em todos os tratamentos (P<0,05), reduzindo de 13,54±0,02% (sem fitase) para 10,59±0,10% (1.500FTU kg-1). A inclusao de niveis crescentes de fitase na dieta, ate 1.500FTU kg-1, melhora o desempenho e as caracteristicas de carcaca de alevinos de jundia.

Alimentação de alevinos de peixe-rei (Odontesthes bonariensis) com dietas naturais e artificiais

An experiment was run to evaluate three feeding methods for pejerrey fingerlings, in a complete randomized design with four replications. Each experimental unit consisted of a 20L aquarium and 20 three days old fingerlings. For six weeks, three times a day, fish received the following diets: T1= mash diet; T2= mash diet + zooplankton; T3= zooplankton. Results showed that zooplankton promotes better fingerlings growth and survival. Fish fed with mash diet showed significantly lower growth and survival, but acceptable considering actual status of nutrition studies for pejerrey.

Probiotic actions of Bacillus cereus var. toyoi and Saccharomyces boulardii in silver catfish (Rhamdia quelen) larvae culture

The objective of this study was to evaluate the use of Bacillus cereus var. toyoi and Saccharomyces boulardii as probiotics to improve Rhamdia quelen culture. Six hundred larvaes (0.16±0.07 g) were divided in three replicate tanks (25-L recirculation, 20 oC, photoperiod of 12 h light/12 h darkness) per treatment and were randomly assigned to the following treatments: Bacillus cereus var. toyoi; Saccharomyces boulardii; B. toyoi and S. boulardii; and control (without probiotic addition) for a period of 30 days. The fish were fed five times daily (56% crude protein - Supra alevino inicial®) and the probiotics were applied in water once a day. The doses of probiotics were 5 × 108 and 2 × 109 CFU (colony forming unit)/mL for B. cereus var. toyoi and S. boulardii, respectively. Both probiotics have an inhibitory effect in vitro against Vibrio carchariae and are able to grow in media prepared with fishery water; however, no effect was observed on growth parameters when they were administered to Rhamdia quelen larvae.

Utilização de farinha de silagem de pescado em dietas para o jundiá na fase juvenil

This study evaluated the productive performance and carcass yield of jundia (Rhamdia quelen) fed with different fish dregs chemical silage flour concentrations in substitution to the sugar cane yeast in a diet based on vegetable ingredients (control diet). Animals with initial weight of 48.11±5.54g were distributed in 5 treatments with 3 replicates, in a completely randomized design. Each observation unit consisted of a 1,000 liter polipropilene tank, with 200 liters of water, with 9 animals, in a thermo-regulated system with water recirculation. During 75 days, twice daily (9h and 17h) the following diets were offered, in the proportion of 7% total biomass: 0% (control), 12.5%, 25%, 37.5% and 50% of silage flour. Results showed a quadratic effect (P<0.05) for inclusion levels of fish silage flour on final weight, weight gain, total length and specific growth rate. The inclusion of 30-35% of fish dregs chemical silage flour in the diet, results in better production performance of jundia juveniles without affecting the survival and the water quality.

Parâmetros eritrocitários do jundiá (Rhamdia quelen) submetido à dieta com diferentes níveis de proteína

Silver catfish is a species of economic interest for the southern Rio Grande do Sul region, Brazil, being well adapted to different environments and artificial diets, showing easy management and good commercial acceptance. Good nutritional status is a determinant factor in fish development. Difference in formation of blood cells is dependent of diet manipulation. The objective of this study was to evaluate the effect of a diet with different protein levels on erythrocytic parameters of silver catfish. Ninety (90) fish were used with an average standard length of 20.01±1.28cm and average weight of 131.4±25.9g distributed in three 1,000L tanks, containing three baskets (80L) each, with three levels of crude protein (30, 40 and 50%). Animals were sampled every two weeks during 45 days. After anesthetization blood was collected through caudal puncture using needle and syringe containing EDTA at 10%. Blood analyses corresponding to the erythrocyte series were performed through automatic counter. Proteic level of diet influences erythrocytic parameters, especially the total number of erythrocytes, hemoglobin rate and hematocrit. The level of 50% CP showed best stimulation of erythropoiesis.

Crescimento e sobrevivência do catfish de canal (Ictalurus punctatus sp) e jundiá (Rhamdia sp) no outono-inverno do Rio Grande do Sul

O catfish e um peixe de couro, com habito alimentar onivoro, nativo dos Estados Unidos, tendo despertado interesse dos produtores e industrias da regiao sul do Rio Grande do Sul, devido a qualidade da carne, crescimento e facilidade de manejo. O jundia tambem e um peixe de couro com habito alimentar onivoro, apresentando bom desenvolvimento e facil reproducao, sendo necessario avaliar seu potencial em sistemas de producao intensiva. O objetivo deste trabalho foi comparar o desempenho e sobrevivencia do catfish, jundia cinza e albino. O experimento foi realizado na estacao de piscicultura do Chasqueiro, localizada no municipio de Arroio Grande - RS, no periodo de abril a agosto de 2001, tendo a duracao de 135 dias. Utilizaram-se 120 juvenis de catfish (91,8±25,8g), 120 de jundia albino (83,7±20,9g) e 120 de jundia cinza (80,4±12,5g), distribuidos em 3 tanques de terra retangulares, com 180m2, divididos longitudinalmente em tres parcelas, formando um total de 9 divisoes de 60m2 cada. Os peixes foram colocados em uma densidade de 0,6 peixe/m2 da area, e alimentados com racao comercial extrusada (PB 36%) na ordem de 3% da biomassa ao dia. Durante o periodo experimental avaliou-se o ganho de peso, o crescimento e a sobrevivencia dos animais. A temperatura da agua variou entre 11 e 290C, com media de 18,5°C. Os resultados indicaram um ganho de peso no periodo de 40,4; 74,1 e 109,1g e sobrevivencias de 14, 32 e 63% para o catfish, jundia albino e cinza, respectivamente. Conclui-se que o jundia cinza apresentou o melhor desempenho produtivo no periodo analisado.

Dietary phosphorus requirement of pejerrey fingerlings (Odontesthes bonariensis)

To determine the available phosphorus requirement of pejerrey fish, four semi-purified diets were formulated to contain increasing available phosphorus levels (0.90, 2.7, 5.7 and 8.3 g/kg). Each diet was assigned to groups of 10 fish with average weight of 1.26±0.17 g, distributed into a completely randomized design with four treatments and four replications. Fish were fed at a rate of 10% total biomass four times a day for 60 days. The parameters productive performance, body chemical composition and mineral composition of bones and scales were evaluated. The best productive performance of fingerlings was obtained with the diet containing 4.3 g/kg available phosphorus. The average level of 6.3 g/kg available phosphorus promotes better mineralization of bones and scales in pejerrey fish.

Use of adsorbent in diets containing aflatoxin for silver catfish fingerlings

The effects of aflatoxins and one adsorbent (Sodium and calcium aluminum silicate) on silver catfish (Rhamdia quelen) fingerlings were evaluated in this study. Three hundred and sixty fish, with initial weight of 4 g, were raised in a thermo-regulated recirculation water system, during 90 days. Twelve treatments with four aflatoxin levels in diet (0, 150, 250 and 350 µg/kg), with and without adsorbents (0, 0.3 and 0.6%) were tested in three replications. The results showed that the negative effect of aflatoxins significantly reduced the growth and weight gain of fingerlings, proportionately to the increasing levels of aflatoxin in diet, with mortality occurrence. The adsorbent levels in diet did not diminish the effects of aflatoxin action on fish performance due to the low inclusion and also little acceptance of ration in relation to the product palatability. It is concluded that silver catfish fingerlings fed diets containing aflatoxin are susceptible to negative effects, with high losses in growth and weight gain.

Benzocaine and clove oil as anesthetics for pejerrey (Odontesthes bonariensis) fingerlings

Pejerrey (Odontesthes bonariensis) is a native species from Rio Grande do Sul, Uruguay and Argentina where it is of great economic importance for artisanal fishing. One difficulty in laboratory research with pejerrey is related to its sensitivity, as it presents higher basal cortisol levels than other freshwater species. For this reason, the aim of this work was to evaluate the efficiency of benzocaine and clove oil as anesthetics for pejerrey fingerlings. Two experiments were done where fingerlings (57±7.8mm and 1.1±0.44g) were exposed to benzocaine with concentrations between 40mgL-1 and 120mgL-1 and to clove oil with concentrations between 12mgL-1 and 75mgL-1. Survival, anesthesia induction time and recovery time for each pharmaceutics were evaluated. Both benzocaine and clove oil pharmaceutics showed efficiency as anesthetics for pejerrey fingerlings, with negative correlation between the dose of anesthetics and the anesthesia induction time. For benzocaine, the concentrations between 80mgL-1 and 100mgL-1 showed better results, as for clove oil the optimal concentrations were between 25mgL-1 and 50mgL-1. On the other hand, the anesthesia recovery time did not present significant variation on the different concentrations of the tested products. The tested products are highly metabolizable by pejerrey.