Influência do melaço no cultivo intensivo do camarão Litopenaeus vannamei na fase berçário sem renovação de água com diferentes relações carbono/nitrogênio

Abstract

This work investigated the effect of molasses addition in different C:N ratios on the water quality and growth performance of the Litopenaeus vannamei shrimp during the nursery phase without water exchange. A randomized experimental design was applied with three treatments and four replicates. Two treatments with daily molasses addition of 25:1 (25M) and 15:1 (15M) C:N ratio and one control with no carbon source addition (0M). Twelve (800 L) fiber glass tanks were stocked with 6.25 post-larvae/L (mean weight < 0.01 g) corresponding to 5000 post larvae/tank. Shrimps were fed with a 40% crude protein commercial diet offered at 08:00, 11:00, 14:00 and 17:00. The feedding rate varied from 50 to 15% of the shrimp biomass from the beginning to the end of the culture. The water temperature, dissolved oxygen and pH were measured daily whereas transparency and salinity were measured weekly. The 25:1 and 15:1 C:N ratios showed lower (p<0.05) pH levels (7.9) when compared to treatment 0M (pH 8.1). Molasses addition resulted in lower (p<0.05) water transparency. After 42 culture days the shrimp final weight in the treatments 25M (532.0 mg) and 15M (540.0 mg) were higher (p<0.05) than 0M treatment (417.8 mg). Shrimp survival was higher in all treatments (77.9 a 90.0%), with no signifincant differences (p>0.05). Thisstudy indicates that the molasses can be used as carbon source in order to increase C:N ratio, improving the water quality and L. vannamei growth performance with no water exchange.