Effects of Early Weaning on Growth and Digestive Enzyme Activity in Larvae of Sea Bass (Dicentrarchus labrax L.)

Abstract

The influence of early weaning on digestive enzymes, growth, and survival in sea bass larvae were investigated. Larvae were reared in a closed sea water system and first fed Artemia nau- plii eight days after hatching. Three weaning periods were compared by introducing a micropar- ticulate diet on day 15, 20, or 25. The control continued to be fed only Artemia. The lowest growth and survival rates were obtained in the 15-day group while the highest were in the 25- day group. After weaning, protease activities (trypsin, chymotrypsin, elastase, pepsin) dropped in all groups, indicating malnutrition. Amylase activity slightly increased in all experimental groups due to the higher starch content in the microparticulate diet than in Artemia and the absolute and relative lipid contents were lower in groups fed the microparticulate diet. Lipase activity suddenly dropped after weaning but slightly rose from day 35 until the end of the exper- iment (day 40). Due to decreased larvae development, survival, and digestive enzyme activity, weaning at 20 days after hatching, synchronous to formation of the stomach and enzymatic activity, is strongly recommended.