Evaluation of the feeding consumption and exoskeleton texture of the marine shrimp Litopenaeus vannamei (Crustacea: Penaeidae) in commercial cultivation, during the molt cycle

Abstract

The objective of the present work was to evaluate, in commercial cultivation, the influence of the shrimp molt cycle stages in the feed consumption, and to correlate the texture of their exoskeleton with the setogenesis identification method. The study was realized in a shrimp pond, located 50 kilometers to the south of Natal City, in the coast of Rio Grande do Norte State from Dec. 2002 to Apr. 2003. A total of 125 shrimps were collected at the pond, three times per week and in five distinct points. During the study, it was obtained the length (mm), weight (g), moulting cycle stages and texture of the exoskeleton of each specimen collected. In a cycle of 119 days, shrimp increased 5.0 mm and 1.0 gram on the average per week, being harvested with 118.07 mm and 13.96 grams. The duration of the stages of the complete molt cycle, estimated through spectral analysis of Fourier, ranged from 10.41 to 13.07 days. The index of correlation of Pearson indicated positive correlation between the soft texture of the exoskeleton and the stages A (r=0.96), D₂ (r=0.57) and D₃ (r=0.42) and between the normal texture and the stage C (r=0.83). In the conditions in those this study was realized, it was concluded that in commercial ponds there exists a synchrony of the shrimps with regard to the moulting cycle, and that the exoskeleton texture can be used as a method for the determination of the moulting period, since complemented by the method of the setogenesis.