ABSTRACT In order to optimize the performance and reduce costs in the larviculture of ornamental carp (Cyprinus carpio) in a recirculating aquaculture system, different feeding strategies were tested. For this, two experiments were carried out both under controlled conditions in a greenhouse, in a recirculating aquaculture system with a physical particle filter, biofilter, and filtering by ultra-violet irradiation. In the first experiment, measurements of Artemia nauplii were tested in the initial exogenous feeding of larvae at concentrations of 100, 200, 400, 600, 800 and 1,000 Artemia nauplii per larvae. In the following experiment, different protocols were tested for initial feeding for larvae. At this stage, were used: live food (Artemia nauplii) and inert (powder meal), used separately and simultaneously, and increases in the number of Artemia nauplii were also tested, offered at different times of cultivation. In the first experiment, the amount of 600 Artemia nauplii for larvae demonstrated to be the best option as it generated significant growth and the cost was less than that observed with the use of 800 and 1000 Artemia nauplii per larvae. The second experiment demonstrated that the feeding strategy with live food more commercial inert feed provided the best growth performance for ornamental carp larvae. The need to fix the amount of live food during the cultivation, probably due to the high specific growth rates observed during the larval stage also became evident.

Oligosarcus argenteus é uma espécie pertencente à subfamília Acestrorhynchinae, restrita à América do Sul, sendo comumente encontrada nas várias bacias hidrográficas brasileiras, em ambientes lóticos e lênticos, onde se reproduzem. Com o objetivo de estudar a biologia reprodutiva de machos desta espécie, vários parâmetros morfológicos foram analisados durante um período de 24 meses, assim como foram caracterizados os diferentes estádios de maturação testicular. Estes foram descritos, considerando-se exemplares adultos, em: Estádio I - Maturação Inicial, Estádio II - Maturação Intermediária e Estádio III - Maturação Final. Pela freqüência bimestral das células germinativas e dos estádios de maturação gonadal, a época de reprodução foi determinada.

Oligosarcus argenteus belongs to the Acestrorhynchinae subfamily, being restricted to South America, and found in several Brazilian hydrographic basins, in lotic and lentic environments, where they are able to reproduce. With the purpose of studying the reproductive biology of the males from this species, many morphological parameters were analyzed during a 24 month period, as well as characterizing the different testicular maturation stages. A maturity scale, with three stages (I - Initial Maturing, II - Intermediate Maturing, III - Final Maturing) was proposed for the adult males of Oligosarcus argenteus. The reproductive period was established by the bimonthly frequency of spermatogenesis and by the gonadal maturation stages.

Foram realizados dois experimentos com o objetivo de comparar técnicas de digestibilidade de nutrientes de alimentos para peixes, com o uso dos indicadores externos (óxido crômico e carbonato de bário) e internos (cinza insolúvel em ácido, cinza insolúvel em detergente ácido, fibra bruta e fibra detergente ácido) e com a técnica de determinação direta. Tambaquis com 100 g receberam, no primeiro experimento, fubá de milho e, no segundo, farelo de soja. O óxido crômico e o carbonato de bário são indicadores externos efetivos para estimar os coeficientes de digestibilidade dos alimentos para tambaquis. A fibra bruta e a fibra detergente ácido apresentaram baixa recuperação e não estimaram de forma consistente os coeficientes de digestibilidade dos alimentos para tambaquis, subestimando-os. A cinza insolúvel em ácido e a cinza insolúvel em detergente ácido apresentaram alta porcentagem de recuperação e estimaram de forma consistente os coeficientes de digestibilidade dos alimentos para tambaquis, quando presentes no alimento em teores acima de 3,8% e 3,1%, respectivamente. A técnica de determinação direta foi eficiente para estimar os coeficientes de digestibilidade dos alimentos para tambaquis.

Two experiments were carried out aiming to compare techniques of digestibility of fish food nutrients, by using external indicators (chromic oxide and barium carbonate), internal indicators (HCl-insoluble ash, acid detergent insoluble ash, crude fiber and acid detergent fiber) and the direct determination technique. Corn meal was used in the first experiment and soybean meal was used in the second one; both used 100 g tambaquis. Chromic oxide and barium carbonate are effective external indicators for estimating the digestibility coefficients of feedstuffs fed to tambaquis. Crude fiber and the acid detergent fiber present a low recovery and do not estimate accurately the digestibility coefficients of feedstuffs for tambaquis and also underestimate them. The insoluble ash in acid and the insoluble ash in detergent acid showed high recovery percentage and accurately estimated the digestibility coefficients of feedstuffs fed to tambaquis, when showed contents higher than 3.8 and 3.1, respectively. The direct determination technique was efficient to estimate the digestibility coefficients of the food given to the tambaquis.