ABSTRACT
The aim of this study was to evaluate three stocking densities (20, 40 and 60 larvae L-1), and two daily prey concentrations (400 and 700 Artemia nauplii larvae-1) during the first seven days of active feeding (first phase). In the second phase was evaluate the effect of the different feeding regimes: fasting, dry diet (55% crude protein), Artemia sp. and mixed feeding (Artemia sp. plus dry diet), after 17 days of active feeding on Rhinelepis aspera larviculture. In the first phase, growth was affected only by prey concentration. In the second phase, the dry diet induced higher growth rates than fasting, but lower growth rates than the other treatments. The acceptance of the dry diet was evidenced by an increase in the growth rate from 4.6% day-1 in the first five days to 10.7% day-1 in the following five days of feeding. Survival was similar among dry diet, mixed feeding and Artemia nauplii treatments. R. aspera larvae can be reared during the first seven days of active feeding at a density of 60 larvae L-1, after which they can be fed with a commercial dry diet.
ABSTRACT
Experiments in the cultivation or ecological with fish larvae, invariably use the length and weight with parameters. Therefore, this experiment was accomplished with larvae of Lophiosilurus alexandri pacamã aiming at to determine some sources of mistakes sampling in the measurement of the size and of the weight of fish larvae. It was evaluated five possible sources of mistakes then. The first was the mistake in the measure of the lengths total and standard, due sharpness of two observers" measurement. The second the mistake in the measure of the lengths total and standard, due to the proportionate shrink for the fixative formomalin to 10%. The third party was the mistake due two forms of drying of the larvae in the obtaining of the biomass. The fourth experiment was on the influence of the size and of the grouping of the larvas in the obtaining of weights. Finally the last tested the alteration of the biomass due to the time of permanence of the larvae in the balance. The importance can be verified of to determine and to accomplish an sampling protocol for measurements of fish larvae. For they present size and weight reduced, a small variation in the condition of the mensure, it can alter the result significantly, because significant alterations were verified above for the tests referred.
Trabalhos com larvas de peixes, sejam de cultivo ou ecológicos invariavelmente empregam o comprimento e o peso como parâmetros. Assim sendo, este experimento foi realizado com larvas de Lophiosilurus alexandri pacamã objetivando determinar algumas fontes de erros amostrais na medição do tamanho e do peso de larvas de peixes. Avaliou-se cinco possíveis fontes de erros. O primeiro foi o erro na medida dos comprimentos total e padrão, devido a acuidade de medição de dois observadores. O segundo, foi o erro na medida dos comprimentos total e padrão, devido ao encolhimento proporcionado pelo fixador formalina a 10%. O terceiro foi o erro devido a duas formas de secagem das larvas na obtenção da biomassa. O quarto experimento foi sobre a influência do tamanho e do agrupamento das larvas na obtenção de pesos. Por fim, o quinto teste observou a alteração da biomassa devido ao tempo de permanência das larvas na balança. Pôde-se verificar a importância de se determinar e cumprir um protocolo de amostagem para medições de larvas de peixes. Por apresentarem tamanho e peso reduzidos, uma pequena variação na condição da mensuração, pode alterar substancialmente o resultado, pois alterações significativas foram verificadas para os testes acima referidos.