Pirarucu, Arapaima gigas, is a carnivorous freshwater fish that exists along the Amazon Basin. This study investigated the effect of stocking density on growth performance and economic return of pirarucu in cages. Fish were stocked at densities of 10 or 12.5 fish/m 3 in 4.0-m 3 cages installed in Sítios Novos Reservoir (Ceará State, Brazil), with three replicate cages for each density. Fish were fed a formulated diet containing 40% crude protein and 14.2 MJ/kg of feed and cultured for 140 days. The following physicochemical parameters of the water were always at satisfactory levels for fish culture throughout the experiments: water temperatures ranged from 26.3 to 30.2°C, DO 3.2 to 7.7 mg/L, pH 6.9 to 7.7 and transparency 100 to 130 cm. Survival was high and ranged between 100.0% and 94.7 ± 5.0% in cages at 10 and 12.5 fish/m 3 , respectively. Density significantly affected (P b 0.05) final mean weight (2630.4 ± 213.7 and 2138.0 ± 148.2 g) and weight gain (2516.9±202.0 and 2043.1±142.9 g). In contrast, specific growth rate (2.25±0.09 and 2.22±0.06%/day), feed conversion ratio (1.2±0.1 and 1.2±0.2) and production (26.3±2.1 and 25.4±2.6 kg/m 3 ) were not significantly (P>0.05) affected by stocking density. Economic analysis was emphasized mostly on sales price and pirarucu juveniles and feed costs. The total costs of production were estimated at US$4.52/kg and US$5.31/kg for stocking densities of 10 fish/m 3 and 12.5 fish/m 3 , respectively. At a local market price of US$5.55/kg, the model used suggests that a commercial enterprise can be profitable only for density of 10 fish/m 3 . Furthermore, the economic viability of implementing of pirarucu culture in cages was analyzed using profitability indicators such as internal rate of return (IRR), net present value (NPV) and payback period. The high survival, very fast growth and moderated production rates of pirarucu stocked demonstrate that cages are a viable alternative method to standard ponds for the commercial production of pirarucu. The economic indicators appear to be attractive, thus pirarucu cage culture can become a profitable industry.

The effect of salinity on survival, growth, haematological parameters and osmoregulation was evaluated in tambaqui. This study addressed two questions. Firstly, tambaqui (33.9 AE 3.4 g) reared in freshwater were subjected to gradual increases in salinity until 100% mortality. Two daily increments of salinity were tested with three replicates: 1 and 2 g L À1 day À1 , while control group was kept in freshwater. For 1 g L À1 day À1 , the first mortality appeared from a salinity of 11 g L À1 and the last dead fish was observed at a salinity of 20 g L À1 , whereas for 2 g L À1 day À1 , the mortalities occurred only between 20 and 22 g L À1 . The main sub-lethal effects observed were food intake stopped, erratic swimming behaviour, increased mucus production and the dark pattern of pigmentation that appeared at 13 and 16 g L À1 for both treatments. Secondly, juveniles (57.4 AE 6.3 g) were reared at 0, 5, 10 and 15 g L À1 , in triplicate, for 84 days. At the end of the experiment, the results indicated that the survival, growth, haematological parameters and osmoregulatory of fish were significantly affected by salinity. Survival was unaffected by 10 g L À1 , whereas higher salinity (15 g L À1 ) had a detrimental effect. Differences in final weight, specific growth rates (SGR) and mean daily feed intake (MDFI) among treatments were significant. There were no significant trends in feed conversion rate (FCR) at salinities of 0, 5 and 10 ppt. In these salinities, FCR ranged between 1.2 AE 0.1 and 1.3 AE 0.1, whereas FCR at salinity of 15 g L À1 increased to 5.8 AE 4.4. At the end of the experiments, analysis of blood revealed that all haematological parameters were affected by increase in salinity. From the present investigation, it can be concluded that exposure to salinity significantly affects the survival, growth and physiological response of tambaqui.

Influence of stocking density on water quality and growth performance in production of juvenile pirarucu, Arapaima gigas, in irrigation canals Influência da densidade de estocagem na qualidade da água e na performance de crescimento na produção de juvenis de pirarucu, Arapaima gigas, em canais de irrigação

The culture of Penaeus vannamei in low-salinity waters is a recent development in Brazilian Northeast. The purpose of this study was to investigate the effects of NaCl dietary supplementation on shrimp growth, survival, haemolymph osmolality and total hemocyte counts. In trial 1, earthen pond-reared shrimp ranging from 5 to 20 g were sampled at intervals for determination of haemolymph osmolality. Haemolymph osmolality was not influenced by the increased weight of shrimp. Juveniles shrimp (5-20 g) haemolymph osmolality were then evaluated 24 h after they had been transferred from pond water (0.5 ppt) to the seawater (35 ppt). Shrimp haemolymph osmolality increased with external salinity and ranged from 661.0 ± 25.2 mOsm/kg (D1) and 916.9 ± 40.1 mOsm/kg (D4). In trial 2, shrimp reared in low-salinity water (0.3-0.5 ppt) were distributed into five groups (control, D1, and treatments, D2, D3, D4 e D5) with four replicates. Diets consisted of the basal diet supplemented with 0 g/kg, 5 g/kg, 10 g/kg, 20 g/kg, and 40 g/kg of NaCl, respectively. After 22 days, differences in survival, final weight, specific growth rates (SGR) and absolute growth rate (AGR) among treatments were significant. However, there were no significant trends in haemolymph osmolality and shrimp total hemocyte counts within the five tested groups.

ABSTRACT. The present work aimed to obtain a mathematical expression to calculate the amount of EDTA required to produce calcium-free and low-calcium water ([Ca 2+ ] < 5 mg L -1 ). Initially, a pilot test was carried out to confirm the effectiveness of EDTA as a chelating agent of waterborne calcium and to evaluate its effect on water pH. Five application rates of Na-EDTA (25, 50, 75, 100 and 125 mg L -1 ) were tested. The concentration of calcium in water was determined initially (before the application of EDTA) and after one hour. Linear regression analysis was performed to find out the relationship between the desired calcium concentration in water and the required EDTA: initial calcium hardness ratio. The expression ŷ = -0.0911x + 3.3628 (R² = 0.933) was derived from the linear regression analysis carried out, in which x represents the desired calcium concentration in water and y the required EDTA: initial calcium hardness ratio. ) para experimentação em aquicultura. Inicialmente, realizou-se teste-piloto para confirmar a efetividade do EDTA como agente complexante do cálcio presente na água e avaliar seu efeito no pH da água. No teste principal, cinco taxas de aplicação de Na-EDTA (25, 50, 75, 100 e 125 mg L -1 ) foram avaliadas. A concentração de cálcio da água foi determinada inicialmente (antes da aplicação de EDTA) e após 1h. Análise de regressão linear foi feita para se descobrir a relação entre a concentração desejada de cálcio na água e a relação EDTA/dureza cálcica inicial da água necessária. A expressão ŷ = -0,0911x + 3,3628 (R² = 0,933) foi obtida a partir da regressão realizada na qual x representa a concentração desejada de cálcio na água e y a relação EDTA/dureza cálcica inicial da água.Palavras-chave: EDTA, dureza cálcica, piscicultura.

O cultivo de Penaeus vannamei em águas oligohalinas tem sido um desenvolvimento recente na região Nordeste. O objetivo deste estudo foi investigar os efeitos da suplementação de NaCl em dietas no crescimento, sobrevivência, osmolalidade da hemolinfa e contagem total de hemócitos dos camarões. No experimento 1, camarões cultivados em águas oligohalinas, com peso variando entre 5 a 20 g, foram utilizados para a determinação da osmolalidade da hemolinfa, não tendo diso influenciada pelo aumento do peso do camarão. Após aclimatação em água do mar (35 ppt), a osmolalidade da hemolinfa foi avaliada em camarões com peso entre 5-20 g, tendo sido incrementada para a salinidade da água do mar (35 ppt), variando de 661,0 ± 25,2 mOsm/kg (D1) a 916,9 ± 40,1 mOsm/kg (D4). No experimento 2, camarões cultivados em águas oligohalinas (0,3-0,5 ppt) foram distribuídos em cinco tratamentos (D1, D2, D3, D4 e D5), com quatro repetições. As dietas consistiram de uma dieta basal suplementada com 0 g/kg, 5 g/kg, 10 g/kg, 20 g/kg e 40 g/kg de NaCl, respectivamente. Após 22 dias, os parâmetros de sobrevivência, peso final, as taxas específicas de crescimento (SGR) e taxa de crescimento absoluto (TCA) apresentaram diferenças significativas entre os tratamentos. No entanto, não houve diferenças significativas na osmolalidade da hemolinfa e contagem total de hemócitos dos camarões distribuídos nos cinco grupos. Palavras-chave: Camarão, água de baixa salinidade, modificação da dieta, osmolalidade da hemolinfa.

Brazil was the third largest producer of white shrimp in Latin America, with 75,000 tons and R$ 600 million, in 2012. The present work focused on the impacts of the IMNV pathogen, the anti-dumping action imposed by USA and the exchange rate appreciation of Brazilian currency in marine shrimp culture in a semi-intensive system in Northeastern region and also on the identification of options for sustainable production. Data were collected on shrimp farms (Compescal and Aquafort) at Ceará state. During the period from 2003 to 2007, these factors affected directly the competitiveness of Brazilian farmed shrimp exportation. However, in 2007 the shrimp producers started to sell on domestic market, which made possible to increase their production, revenue, income and profit levels.