Alimento vivo na dieta de larvas do surubim híbrido (Pseudoplatystoma reticulatum x P. corruscans) em viveiros escavados: bases ecológicas para estudos do crescimento de fases iniciais

Abstract

Natural food production via fertilization of fish ponds is a common practice in fish hatchery. However, there are many questions to be answered, specially the lack of a specific dietary protocol of carnivorous fish, wich is a strong constraint for the production, because of the lack of knowledge about the ecology of growth during the fish’s early stages. The aim of this study was to evaluate the diet and growth of post-larvae of hybrid surubim on natural feeding period compared to the availability of food in the environment. The study was carried out in three fish ponds (V1, V2 e V3), using semi-intensive system in a fish farm in Dourados-MS. After initial fertilization and complete filling of ponds, zooplankton samples were collected with a plankton net, zoobenthos with a Petersen’s dredger and 10 post-larvae of hybrid surubim, every three days, in a total of four samples in each pond. The diet was composed by Moina minuta, Chironomidae larvae, other invertebrates and fish (cannibalism). We found a better growth of the post-larvae in the V1, wich was associated with higher densities of zooplankton and higher consumption of Chironomidae. Although rotifers were the most abundant organisms (80% of zooplankton collected), the post-larvae of hybrid surubim fed up selectively Moina minuta. Among the bentic invertebrates Chironomidae larvae represented more than 60% of taxa collected, and it was the second most consumed item, especially from the third day of sampling, when the post-larvae were between 2.0 and 3.5 cm. Cannibalism (presence of congeners in stomach contents) observed especially in V1 increased as the fish grew, decreasing considerably in the last day. The results of this study show that fertilization of ponds in semi-intensive system was efficient in the growth of post-larvae hybrid surubim, and even for early stages, there is selection of food during natural diet.