Physiological responses of tambaqui (Colossoma macropomum) fed diets supplemented with silage from fish and vegetables residues / Respostas fisiológicas de tambaqui (Colossoma macropomum) alimentado com dietas suplementadas com silagem de resíduos de pescado e vegetais

The demand for products to replace high-cost raw materials, such oil and fish meal, in the manufacture of feed for use in aquaculture, while also guaranteeing the nutritional quality of the diets, is increasing. Silage produced with fish and vegetables residues is a low-cost and efficient protein source. The objective of the present study was to evaluate the physiological and biochemical responses of tambaqui fingerlings fed four different levels of silage included in commercial feed with 28% crude protein, over two periods: 45 and 90 days. Each treatment was carried out over three replications, with 10 tambaqui in each 100 L experimental tank. At the end of each established period, blood samples were collected from five animals from each repetition to determine the hematological and biochemical variables. Body weight and total length, hepatosomatic and liposomal indices and hematocrit of specimens fed with diets supplemented with silage did not exhibit significant changes in both assessment period. After 45 days of feeding, the hemoglobin concentration increased when tambaqui were fed a diet including 20% silage. The red blood cell count, mean corpuscular volume and mean corpuscular hemoglobin did not change between treatments in either period. The total protein concentrations increased significantly in the plasma of tambaqui fed with diets with the inclusion of 5 and 10% of silage, evaluated after feeding for 45 days. It was found that the groups which had silage included in their diet did not exhibit significant alterations in the evaluated parameters, and the diet was therefore not consider harmful to the health of tambaqui. Therefore, the use of silage as a feed supplement during tambaqui farming is a sustainable alternative for producers, as it leads to a reduction of impacts of fish and vegetables waste disposal.

A procura por insumos que substituam produtos de alto custo, como óleo e farinha de peixe, na fabricação de rações para uso na aquicultura é crescente, sendo necessário garantir a qualidade nutricional das dietas. A silagem produzida a partir de resíduos de pescado e de vegetais apresenta-se como uma alternativa de baixo custo e eficiente fonte proteica. O objetivo do presente estudo foi avaliar as respostas fisiológicas e bioquímicas de alevinos de tambaqui alimentados com quatro níveis de inclusão de silagem em ração comercial com 28% de proteína bruta, em dois períodos: 45 e 90 dias. Cada tratamento foi realizado em três repetições, com 10 tambaquis em cada caixa experimental de 100 L. Ao término de cada período estabelecido, amostras sanguíneas foram coletadas de cinco animais de cada repetição para determinação das variáveis hematológicas e bioquímicas. Peso, comprimento total e índices hepatossomático e lipossomático de espécimes alimentados com silagem não mostraram alterações significativas em ambos os períodos de avaliação, bem como os valores de hematócrito. A concentração de hemoglobina de tambaqui após 45 dias de alimentação aumentou quando foi fornecida dieta com inclusão de 20% de silagem. A contagem de eritrócitos, volume corpuscular médio e hemoglobina corpuscular média não apresentaram alterações entre os tratamentos, em ambos os períodos. As proteínas totais aumentaram significativamente no plasma de tambaquis que receberam dietas com inclusão de 5 e 10% de silagem, avaliados após 45 dias de alimentação. Evidenciou-se que os grupos com inclusão de silagem na dieta não apresentaram alterações significativas nos parâmetros avaliados, assim não sendo prejudiciais à higidez do tambaqui. Portanto, o uso da silagem como suplemento alimentar durante o cultivo do tambaqui é uma alternativa sustentável para produtores, por promover a redução do descarte de resíduos de pescado e da agricultura.

Selenium alleviates biological toxicity of thiamethoxam (TMX): Bioaccumulation of TMX, organ damage, and antioxidant response of red swamp crayfish (Procambarus clarkii).

Pesticides are important for agricultural development; however, animals involved in rice-fish farming absorb the pesticides used during the farming process. Thiamethoxam (TMX) is extensively used in agriculture and is gradually occupying the market for traditional pesticides. Therefore, this study aimed to investigate whether selenomethionine (SeMet) could affect the survival rate, bioaccumulation of TMX, serum biochemical parameters, lipid peroxidation, antioxidants in the hepatopancreas, and expression of stress genes after exposure of red swamp crayfish to 10 ppt TMX for 7 days. The results showed that the survival rate significantly increased and the bioaccumulation of TMX significantly decreased with SeMet administration (P < 0.05). Furthermore, severe histological damage to the hepatopancreas of red crayfish was observed after exposure to TMX; however, this damage was alleviated after SeMet administration. SeMet also significantly reduced the TMX-induced changes in serum biochemical parameters, malondialdehyde content, and antioxidant enzyme activity in crayfish hepatopancreas (P < 0.05). Notably, analysis of the expression of 10 stress response genes showed that 0.5 mg/kg SeMet might decrease cell damage in the hepatopancreas. Consequently, our findings suggest that higher levels of TMX in crayfish may cause hepatopancreatic cell toxicity, which can be harmful to human health; however, SeMet could mitigate these effects, providing an understanding of pesticide compounds and food safety.

Perceptions and Liking Distortion from Information about the Nutritional Upgrades in Biofortified Seafood Products.

(1) Background: As biofortified fish meat is becoming increasingly available, the use of supplements within fish feed may impact consumers' perceptions and their willingness to pay (WTP) for the product. This study focused on evaluating the sensory liking of, and WTP for, fish produced with fortified feed while understanding the role played by the acquired information on fish fortification. (2) Methods: Hedonic ratings and WTP were measured in an experimental bid. The participants (n = 91) were asked to rate pleasantness and WTP during two different rounds: (i) appearance-information-tasting and (ii) appearance-tasting-information. A total of three fish species (carp, seabream, and trout) were presented to the consumers as being either fortified (with iodine, selenium, and omega-3 fatty acids) or conventional products. (3) Results: For pleasantness, no significant differences were found between the fortified and conventional fish. In contrast, substantial differences emerged when information regarding the products was provided. Providing the relevant information before tasting affected how much the consumers liked the conventional fish, resulting in a preference for it over the fortified fish. Additionally, consumers are willing to pay more for fortified fish, especially when information with respect to fortification is available. Nevertheless, when information about fortification was provided before tasting, the consumer's expectations were not fulfilled. (4) Conclusions: The outcomes of this study clearly indicate that the presence of relevant information impacts how much people like fortified versus conventional fish, as well as their WTP.

Economic, social, and environmental assessment of farming Nile tilapia in net-cages in a reservoir in hot semi-arid region during an extended drought event.

Water reservoirs have been constructed in hot semi-arid regions, which may be used to produce fish. The present study described major features of the economic, social, and environmental characteristics of a net-cage Nile tilapia production system, stocked with 100 and 120 fish/m3, implemented in a reservoir in the hot semi-arid region of Brazil during an extended drought event. The production cycle was reduced from 6-8 to 4 months because of the lack of water in the reservoir. This resulted in the harvest of small fish weighting ~300-350 g that reached a low value in the market. As a consequence, indicators of financial feasibility showed low values, which were not attractive for entrepreneurs. Nevertheless, for both stocking densities, the monthly income was about US$ 1,500.00, which is 5-fold the minimum wage in the region. In general, the activity has a positive social impact, despite the low contribution to development of the local economy and food security because most supply came from outside and fish were sold to distant regions. Various age and ethnic groups were represented among the employees, but the enterprise was operated only by men. Phosphorus accumulations in the reservoir were 2.1 and 2.0 kg/t of fish produced and particulate material accumulations of 110 and 100 kg/t of fish production for 125 fish/m3 and 100 fish/m3, respectively. The study indicated that the Nile tilapia culture in hot semi-arid region is strongly affected by long drought events and adaptations in the planning and management should be done when implementing the systems. However, it seems that the activity has some resilience to still provide food, generate wealth, and promote social development for local population with low environmental impact.

Identifying pollution sources of sediment in Lake Jangseong, Republic of Korea, through an extensive survey: Internal disturbances of past aquaculture sedimentation.

Lake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a "hotspot" site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (13C and 15N) of organic matter suggested that the pollutants in the sediments at the "hotspot" sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.

Ovicidal effect of essential oils of Lippia alba, Lippia sidoides and Lippia gracilis on the acanthocephalan Neoechinorhynchus buttnerae (Eoacanthocephala: Neoechinorhynchidae).

Acanthocephalosis in tambaqui Colossoma macropomum culture is a limiting factor for the production of the species, being the most recurrent, which makes it necessary to develop strategies to control parasitosis even in the early stages of parasite development. This study aimed to elucidate the morphological characteristics of eggs of the acanthocephalan Neoechinorhynchus buttnerae and the ovicidal effect of the essential oils of Lippia alba, Lippia sidoides, and Lippia gracilis. The parasites were collected from hosts naturally infected with N. buttnerae, and the eggs obtained from the female 'parasites' abdominal cavity were added to 12-well plates containing the essential oils at different dilutions. After the eggs (N = 300) were separated and measured (length and width) with the aid of an optical microscope coupled to a digital program, the viability of the treated eggs was monitored 24 h after treatments, L. gracilis essential oil was 100% effective at the highest concentration, whereas L. sidoides essential oil showed over 50% efficacy at 2 mg/ml, reaching 100% efficacy at all higher concentrations. Lippia. alba essential oil did not show satisfactory efficacy in preventing N. buttnerae egg hatching.

Effects of elderflower extract enriched with polyphenols on antioxidant defense of salmon leukocytes

BACKGROUND: In fish farming, the plant extracts containing antioxidant compounds have been added to the diet for enhancing pathogen resistance. In vitro studies evaluating the antioxidant effect of herbal extracts on fish cell models have focused on ROS production and the respiratory burst mechanism. However, the effects on enzymatic antioxidant defense on salmon leukocytes have not been evaluated. This study aims to evaluate the enzymatic antioxidant defense and ROS-induced cell damage in Salmon Head Kidney-1 (SHK-1) cell line exposed to polyphenol-enriched extract from Sambucus nigra flowers. RESULTS: Firstly, the Total Reactive Antioxidant Power (TRAP) assay of elderflower polyphenol (EP) was evaluated, showing 459 and 489 times more active than gallic acid and butyl hydroxy toluene (BHT), respectively. The toxic effect of EP on salmon cells was not significant at concentrations below 120 mg/ mL and no hemolysis activity was observed between 20 and 400 mg/mL. The treatment of SHK-1 cell line with EP decreased both the lipid peroxidation and protein oxidation induced by H2O2, which could be associated with decreasing oxidative stress in the SHK-1 cells since the GSH/GSSG ratio increased when only EP was added. CONCLUSIONS: These results suggest that plant extracts enriched with polyphenols could improve the enzymatic antioxidant defense of salmon leukocytes and protect the cells against ROS-induced cell damage

Physiological activity of Aloe vera in pacu (Piaractus mesopotamicus) inoculated with Aeromonas hydrophila.

Aloe vera is a traditional medicinal plant; however, its use in fish is fairly recent. We evaluated the effects of dietary A. vera on stress, innate immunity, and energy metabolism in pacu inoculated with Aeromonas hydrophila. For 7 days, 192 fish were fed with diets supplemented with 0% (control), 0.5%, 1.0%, and 2.0% of the plant extract and then inoculated with bacteria and sampled 3, 6, and 24 h later. All concentrations of A. vera reduced basal levels of cortisol, and 1.0% reduced cortisol levels more intensely 3 h after inoculation. A. vera increased the basal respiratory activity of leukocytes/RAL (0.5 and 1.0%), increased the serum levels of lysozyme (1.0 and 2.0%) 6 h after inoculation, and increased the activity of the complement system after 3 h. Spleen somatic index/SSI increased with 1.0 and 2.0% A. vera. A. vera also promoted metabolic effects. It increased basal levels of lipids in the liver and muscle, as well as hepatosomatic index (1.0%) and, 3 h after inoculation, prevented the reduction of serum triglyceride (1.0%) and reduced the mesenteric fat (1.0%). Bacterial inoculation increased RAL from 3 to 24 h and lysozyme levels at 24 h, increased serum cholesterol at 24 h, and decreased serum triglyceride from 3 to 24 h, regardless of A. vera. We concluded that A. vera offered for only 7 days had stress-reducing effects, stimulated innate immunity, protected triglyceride levels in blood, lipid depots in the liver and muscle, and directed the energy mobilization to visceral depots.

Anthelminthic potential of the Ficus insipida latex on monogeneans of Colossoma macropomum (Serrasalmidae), a medicinal plant from the Amazon.

INTRODUCTION: Herbal therapy is a potentially beneficial alternative for fish aquaculture, since it may be cheaper and more effective than chemotherapy. The aim of this study was to investigate the in vitro efficacy of Ficus insipida latex on monogeneans of Colossoma macropomum gills. MATERIALS AND METHODS: To evaluate the anthelmintic activity, four concentrations of F. insipida latex (250, 500, 750 and 1000 µL/L) and exposure time to cause immobilization on monogeneans were used. In addition, two control groups, being one with water from the breeding tank and the other with breeding water from the tank + 70% ethyl alcohol were used. RESULTS: At the concentration of 250 µL/L of F. insipida latex, the immobilization of the monogeneans occurred after 4 h of exposure, while at the concentration of 500 µL/L, it occurred after 2 h. At the concentrations of 750 and 1000 µL/L of F. insipida latex, the immobilization of the monogeneans occurred after 1 h and 30 min, respectively. After exposure to 250 µL/L of F. insipida latex, 100% of immobilization of monogeneans was observed within 4 h, to 500 and 750 µL/L, 100% immobilization occurred within 4 h and to 1000 µL/L, 100% mortality occurred after 2 h. CONCLUSIONS: Thus, we recommended the use of 1000 µL/L of F. insipida latex for therapeutic baths in of C. macropomum against monogeneans, after previous test of toxicity.

Nitrogen and phosphorus flux from the production of Nile tilapia through the application of environmental indicators / Fluxo de nitrogênio e fósforo na produção de tilápia-do-nilo (Oreochromis niloticus) a partir da aplicação de indicadores ambientais

Abstract We aimed in this study utilize environmental indicators as a quantitative method to evaluate and discuss the nitrogen (TN) and phosphorus (TP) flux by a production stage grow-out (termination) of Nile tilapia (Oreochromis niloticus) in fishpond. The TN and TP load, the mass balance, the input of TN and TP via feed and the converted nutrients in fish biomass are the environmental indicators applied in this study. During the production cycle (128 days), the system exported 15,931 g TN and 4,189 g TP that were related to the amount of feed supplied (r Pearson = 0.8825 and r = 0.8523, respectively), corroborated by the feed conversion ratio (1.61:1). The indicators showed that 26% TN and 45% TP were reversed into fish biomass, 62% TN and 40% TP were retained in the fishpond, and 12% TN and 15% TP were exported via effluent. The largest contribution of nutrients generated by the system and exported via effluent was observed in phase III and IV. This result is supported by the feed conversion ratio 2.14 and 2.21:1 obtained at this phase, a fact explained by the amount of feed offered and the fish metabolism. Application of environmental indicators showed to be an efficient tool to quantify flux of TN and TP produced during the grow-out period of Nile tilapia and therefore, guide management practices more sustainable. Concerning the environmental sustainability of the activity the implementation of best management practices such as the better control of the feed amount offered would lead to a smaller loss of TN and TP to the water. Furthermore, the use of better quality feeds would allow greater nutrient assimilation efficiency.

Resumo Nós objetivamos neste estudo, utilizar indicadores ambientais como método quantitativo para avaliar e discutir sobre o fluxo de nitrogênio (TN) e fósforo (TP) na etapa final de crescimento (terminação) de tilápia-do-nilo (Oreochromis niloticus) em viveiro escavado. A carga de TN e TP, o balanço de massa, a entrada de nutrientes via ração e o TN e TP convertido em biomassa de peixe foram os indicadores ambientais utilizados neste estudo. Durante o ciclo produtivo (128 dias), o sistema exportou 15.931 g NT e 4.189 g PT os quais foram relacionadas às quantidades de alimento fornecido (r Pearson = 0,8825 e r = 0,8523, respectivamente), corroborada pela conversão alimentar (1,61:1). Os indicadores evidenciaram que 26% NT e 45% PT foram revertidos em biomassa de peixe, 62% NT e 40% PT ficaram retidos no viveiro e 12% NT e 15% PT foram exportados via efluente. O maior aporte de nutrientes gerado pelo sistema e exportado via efluente foi verificado nas fases III e IV. Este resultado é corroborado pelas taxas de conversão alimentar de 2,14 e 2,21:1 obtida nestas fases, fato explicado pela quantidade de ração ofertada e pelo metabolismo dos peixes. A aplicação dos indicadores ambientais mostrou ser uma ferramenta eficiente para quantificar o fluxo de TN e TP produzidos durante a etapa final de crescimento de tilápia-do-nilo e com isso orientar práticas de manejo mais sustentáveis. Com vistas à sustentabilidade ambiental da atividade, a implantação de boas práticas de manejo tais como o melhor controle da quantidade de alimento ofertado levaria a menor perda de NT e PT para a água. Além disso, o uso de rações de melhor qualidade permitiria maior eficiência de assimilação desses nutrientes.

Lamella dissolved air flotation treatment of fish farming effluents as a part of an integrated farming and effluent treatment concept.

Nutrient emissions from fish farming can be reduced by a bag pen, i.e., a floating circular basin which serves simultaneously both as a fish cultivation tank and a swirl separation tank. Solid matter (excreta and uneaten feed) is collected at the bottom of the bag pen and pumped as an underflow to a dissolved air flotation (DAF) unit for nutrient removal. DAF equipped with lamella elements was studied in real conditions. Altogether 3000 rainbow trout females (2.0 kg each) were cultivated. Solid-water mixture was pumped from the bottom of the bag pen to an equalizing basin using a sequence of 2-min pumping followed by a 4-min pause. In some tests the influent was pumped directly and continuously from the bag pen to DAF. The influent quality changed substantially: average suspended solids (SS) and phosphorus (P) concentrations were 290 mg l⁻¹ ± 110 mg l⁻¹ and 3.2 mg l⁻¹ ± 1.2 mg l⁻¹, respectively. When the influent was fresh and P strongly associated with SS, DAF without precipitation chemicals produced up to 86% SS and 83% P removals. The influence of chemical doses was studied using 6.4-29.2 mg Fe l⁻¹ with hydraulic loadings (HLs) of 11.0-11.7 m h⁻¹. SS and P removal did not change substantially and the effluent concentration levelled at 30 mg SS l⁻¹ and 0.20-0.30 mg P l⁻¹, respectively. The lamella DAF, coupled with ferric precipitation, produced up to 90% P and 80% nitrogen reductions. HLs, excluding recycle water flow and lamella projection, up to 21 m h⁻¹ could be used.

A suplementação de vitamina C na estruturação do tecido conjuntivo de melanotência-maçã / Vitamin C supplementation in the structuring of connective tissue of red rainbowfish

Peixes cultivados mostram-se altamente sensíveis a dietas deficientes em ácido ascórbico com sinais clínicos que afetam o desempenho e a comercialização por provocar deformidades. Com objetivo de conhecer os níveis mínimos para a melanotênia-maçã, foram testadas seis rações isoaminoacídicas e isocalóricas com níveis variados de vitamina C ativa. Ao final dos 42 dias experimentais, 36 peixes foram analisados histologicamente quanto à porcentagem de tecido conjuntivo e fibras musculares a fim de determinar a influência da porcentagem de Vitamina C nesses índices. Apesar de as médias serem estatisticamente iguais do ponto de vista quantitativo, qualitativamente os níveis mais altos de vitamina C possibilitaram melhor estrutura tecidual. A desestruturação do tecido muscular é um indicativo da deficiência alimentar com ácido ascórbico...

Farmed fishes are highly sensitive to diets deficient in ascorbic acid with clinical symptoms that affect performance and commercialization for causing deformities. Aiming to meet the minimum levels for red rainbow fish, six isoaminoacid and isocaloric diets with varying levels of active vitamin C were tested. At the end of 42 days experimental period, 36 fishes were histologically analyzed for the percentage of connective tissue and muscle fibers in order to determine the influence of the Vitamin C percentage in those ratios. Although the averages are statistically indistinguishable from the quantitative point of view, qualitatively higher levels of vitamin C allow better tissue structure. The breakdown of muscle tissue is indicative for dietary deficiency of ascorbic acid...

Physiological responses of pacu (Piaractus mesopotamicus) treated with homeopathic product and submitted to transport stress.

BACKGROUND: Pacu (Piaractus mesopotamicus) is a species with great potential for Brazilian fish farming and losses through mortality are common after transport as a direct or indirect result of stress. The use of homeopathic complex is a further option to minimize the various stress factors that can interfere negatively in production. METHODS: After feeding for 10 consecutive days with commercial diet; or diet supplemented with sucrose; or commercial diet supplemented with homeopathic complex, juvenile pacu were placed in a polyethylene bags and transported for four hours with the following treatments: commercial diet (control); commercial diet and homeopathic complex dissolved in the transport water (W + HP); commercial diet supplemented with sucrose (D + SU) and commercial diet supplemented with homeopathic complex (D + HP). Blood was collected before transport (basal), after transport (arrival), 24 and 72 h after transport. The physiological indicators of the stress were blood glucose, cortisol and chloride levels, hematocrit, hemoglobin and total protein. Condition factor and mortality were also determined. RESULTS: Blood glucose increased significantly on arrival, returning to the basal values 24 h after, similarly in all treatments. Plasma cortisol levels were elevated on arrival but not significantly compared to the basal values for fish from W + HP and D + SU groups. Increase in hematocrit and hemoglobin and low plasma chloride levels were observed after transport in all treatments. CONCLUSION: Transport resulted in stress responses in juvenile pacu and the homeopathic complex, administered in the water or diet, did not minimize these responses. Sucrose supplementation altered the cortisol and blood glucose levels, suggesting a moderating effect on these stress indicators.

Influence of a net cage tilapia culture on the water quality of the Nova Avanhandava reservoir, São Paulo State, Brazil / Influência da tilapicultura em tanques-rede sobre a qualidade da água no reservatório de Nova Avanhandava, Estado de São Paulo, Brasil

In order to understand the influence of a net cage tilapia culture on the environment, water quality parameters were investigated during the period between December, 2005 and November, 2007. Three sampling stations were established in the reservoir of Nova Avanhandava (Zacarias, São Paulo State) as follows: upstream of net cage area (P1), in the rearing place (P2) and downstream of net cage area (P3). The mean values of the parameters examined in the water sampling stations were within the standards of water quality recommended by resolution no. 357/2005 of the Conselho Nacional do Meio Ambiente for class 2 freshwater bodies. A significantly higher mean concentration of total phosphorus (p < 0.05) in the P2 (0.035 mg L-1) was the result of the uneaten feed and feces of fish. The average concentration of total phosphorus in P3 was lower (0.015 mg L-1), which was assimilated by the aquatic ecosystem. The frequent monitoring of the water parameters is fundamental, so the producer can adjust the management according to environmental conditions, by reducing fish density or changing feeding rates for example, to mitigate or avoid water quality deterioration.

O comportamento das variáveis da água na área do reservatório de Nova Avanhandava (Zacarias, Estado de São Paulo) com tanques-rede instalados para produção de tilápia foi avaliado no período de dezembro de 2005 a novembro de 2007, para estudar a influência deste sistema de piscicultura no ambiente. Três estações de coleta foram estabelecidas, sendo uma a montante (P1) da área aquícola, outra no centro da piscicultura (P2) e a última a jusante (P3). Os valores médios dos parâmetros da água analisados nas estações de amostragem ficaram nos padrões de qualidade da água recomendado pela Resolução n. 357/2005 do Conselho Nacional do Meio Ambiente para os corpos de água doce classe 2. A concentração média significativamente maior (p < 0,05) de fósforo total na estação P2 (0,035 mg L-1) foi consequência dos restos de ração não ingerida e das fezes dos peixes. Na estação P3, o valor médio da concentração de fósforo total foi menor (0,015 mg L-1), sendo este assimilado pelo ecossistema aquático. O monitoramento frequente das variáveis da água é fundamental para o produtor adaptar seu manejo de acordo com as condições do ambiente, reduzindo densidade ou alterando taxas de alimentação, por exemplo, para mitigar ou evitar a deterioração da qualidade da água.

Substituição do óleo de peixe por óleo de soja em dietas para beijupirá (Rachycentron canadum) / Replacement of fish oil by soybean oil in diets for cobia (Rachycentron canadum)

A substituição do óleo de peixe em dietas para beijupirá (Rachycentron canadum) foi avaliada usando-se cinco proporções de óleo de peixe e soja. Duzentos juvenis (±12g) foram distribuídos aleatoriamente em 20 tanques e alimentados até a saciedade aparente durante 42 dias. À medida que se aumentou o teor de óleo de peixe nas dietas, houve aumento proporcional no desempenho. Os juvenis alimentados com dietas que continham 75 e 100 por cento de óleo de peixe apresentaram ganhos de peso mais altos que os das dietas com 0 e 25 por cento de óleo de peixe, enquanto os alimentados com a dieta com 50 por cento de óleo de peixe apresentaram crescimento intermediário. Não foram observadas diferenças nas concentrações de proteína e lipídio na carcaça dos peixes, mas os teores de umidade e cinzas diferiram entre os tratamentos. A inclusão de teores relativamente altos de ingredientes de origem vegetal diminuiu o consumo alimentar, o que afetou negativamente o crescimento. Os resultados indicam a possibilidade de substituição de até 50 por cento do óleo de peixe por óleo de soja em dietas para juvenis do beijupirá.

The replacement of fish oil for cobia (Rachycentron canadum) in diets was evaluated using five proportions of fish oil:soybean oil. Two hundred juveniles (±12g) were randomly distributed in twenty 480L tanks and fed to apparent satiety twice daily for 42 days. Diets contained 12 percent lipids with different proportions of fish to soybean oils and were therefore named OP0, OP25, OP50, OP75 and OP100 according to the inclusion content of fish oil (0, 25, 50, 75 and 100 percent, respectively). Increasing dietary fish oil levels resulted in higher survival, growth and feed intake. Fish fed diets OP75 and OP100 presented higher weight gain than those fed diets OP0 and OP25, whereas fish fed diet OP50 had an intermediate weight gain. Overall, performance was enhanced at higher contents of dietary fish oil. No significant differences on protein and lipid content of fish carcass were observed, but moisture and ash content differed significantly between treatments. The inclusion of relatively higher contents of plant ingredients affected feed intake, which resulted in lower growth rates. The present results suggest the possibility of replacing up to 50 percent of fish oil with soybean oil in diets for cobia juveniles.