NATURAL FEED OF "CASCUDO PRETO", RHINELEPIS ASPERA AGASSIZ, 1829 (OSTEICHTHYES - LORICARIIDAE), LARVAE IN CULTURE SYSTEM

Abstract

Natural feed of Rhinelepis aspera larvae was studied over the initial thirty-two-days period of life, monitoring the variations of plankton population in four 1,000-liter asbestos-cement tanks weekly fertilized with 50 gram of bird manure over the last twenty days of experiment. Daily samplings of larvae were made in the initial ten days period and every-two-days, and those of plankton were made every-two-days. The analysis of the tank plankton showed that Rotifera, Scenedesmus spp. and eggs formed the groups with higher densities. The following items were found: algae (Diatoms, Chlorococcales, Chlorophyceae, Scenedesmus spp., and Chlamydomonas spp.), anirnals (Rotifera, Arcella spp., Tecameba, Cladocera, Acarina, and Nematoda). Rotifera and Scenedesmus spp. constituted the most important food items of R. aspera in tanks in the initial thirty-two-days period, both occurring with 86.7% (constancy of occurrence) and 57.1% and 40.5% (dominance) in the contents of the digestive tracts analyzed. The most important larvae feed organisms presented significant population densities in the culture tanks.