The present study aimed to determine the dietary lysine requirement for tambaqui (Colossoma macropomum) juveniles, based on growth performance, whole‐body composition, haematological parameters and plasma metabolites. For that purpose, an 81‐day feeding trial was conducted with 150 tambaquis distributed in 15 aquariums (300 L) in a completely randomized design, with five treatments and three replicates. Five diets were formulated and crystalline l‐lysine was added to obtain diets with lysine concentrations of 9.1; 11.9; 14.7; 17.5; and 20.3 g/kg dry diet. Data were subjected to one‐way analysis of variance (p < .05), analyses of broken‐line and second‐degree polynomial regressions were combined to determine dietary lysine requirement. Fish fed 14.9 to 21.0 g/kg lysine showed higher weight gain, specific growth rate and lower feed conversion ratio, viscerosomatic index. In addition, dietary lysine levels of 15.6 and 19.4 g/kg provided higher fish whole‐body deposition of protein and lower deposition of lipid respectively. There were no significant differences in haematological analysis and plasma metabolites of the fish. Thus, according to the second‐order polynomial analysis of a broken‐line response for weight gain, the optimum dietary lysine requirement for tambaqui juvenile was estimated to be 16.1 g/kg dry diet (5.4% dietary protein).

O Arquipélago do Marajó possui potencial natural e mercadológico para o desenvolvimento da piscicultura. Contudo, informações referentes aos aspectos produtivos e econômicos da piscicultura nessa região ainda são incipientes, o que inviabiliza as tomadas de decisão que possibilitem seu crescimento. Assim, objetivou-se com o presente estudo analisar os aspectos produtivos e econômicos da piscicultura no Arquipélago do Marajó, Pará, Brasil. Foram utilizados dados do Instituto Brasileiro de Geografia e Estatística (IBGE) referentes à Produção da Pecuária Municipal de 2014 a 2018 e do Censo Agropecuário de 2017 dos municípios integrantes do Arquipélago do Marajó, visando levantar informações sobre o comportamento da produção, principais espécies cultivadas, número de pisciculturas em operação e preços praticados por espécie. A produção total da piscicultura aumentou em 487,9%, saindo de 18,2 toneladas em 2014 para 107,0 toneladas em 2018. O tambaqui é a espécie mais produzida e também a mais frequente nas pisciculturas do Arquipélago do Marajó. O curimatã, tambacu/tambatinga e pirapitinga têm registros de produção somente no município de Breves, sendo este o município que apresenta o maior número de pisciculturas em operação na região. Os preços praticados foram superiores à média estadual, com o preço de tambaqui em Curralinho e tambacu/tambatinga em Breves apresentando incremento maior do que a inflação do período. O Arquipélago do Marajó se apresenta como promissor para o desenvolvimento da piscicultura, mas o aproveitamento de suas potencialidades depende de políticas públicas estaduais eficientes e profissionalização e organização dos empreendimentos, visando o incremento de sua competividade no estado do Pará.

No abstract

Pyrrhulina brevis is an endemic fish from the Amazon basin that is valued in the ornamental fish market. In larviculture, fish are very sensitive to stressors and have a high mortality rate. Salinized water may provide more energy to overcome stress and feeding frequency is an important strategy to improve productive performance. Therefore, the aim of this study was to evaluate the best feeding frequency and the best level of water salinization for larval development of P. brevis. A total of 360 post-larvae of P. brevis (5.26 ± 1.65 mg, 5.57 ± 0.68 mm) were randomly distributed in 36 aquariums (1 L) in a 3x4 factorial scheme, to evaluate three concentrations of salt in water (0, 1 and 2 g L-1) and four feeding frequencies (once, twice, three and four times a day). We offered 150 Artemia nauplii per day and per post-larvae during 15 days. The fish kept at 1 g L-1 salinized water, and those fed 3 and 4 times a day presented significantly greater final length and weight, weight gain, and specific growth rate for length and weight. An interaction between salinized water and feeding frequency was observed for survival rate. We conclude that, during the initial rearing phase of P. brevis, feeding frequency of three times a day and salinized water at 1 g L-1 is recommended.

This study aimed to analyze the cost of production and the profitability of creating pirarucu in nurseries excavated in different economic scenarios in the state of Pará. The price of inputs was consulted in the municipalities of Igarapé-açu, Castanhal and Goianésia, while the price of the first commercialization of the product was obtained in Quatipuru and Paragominas, between January to August 2018. Subsequently, four economic scenarios were projected, varying the apparent feed conversion and the price of the product. It was concluded that the creation of pirarucu in excavated nurseries, with feed as the only source of food, does not represent a profitable investment in Pará.