Sea bass, sea bass (Dicentrarchus labrax) is a significant breeding species in the Mediterranean. Females reach sexual maturity at the age of 3-5 years, while males mature at the age of 1-2 years. The growing cycle from young to consumer size (exceeding 300 g), in 2 or 3 years enters with full maturity, which means that the gonads mature. Total food consumption in aquaculture must provide sufficient energy for maintenance metabolism, growth metabolism and reproductive cell production metabolism. Production results are assessed through survival, growth and food consumption. Growth and food consumption are closely related, and feeding efficiency is assessed by food conversion factor. In addition to somatic tissue, growth in sexually mature individuals includes gonadal growth. In the phase of preparation for spawning, the growth of gonads contributes to the total growth of biomass, while spawning loses this growth. Loss of biomass due to spawning has an impact on the change in the record status of cultivated biomass and on the increase of effective / economic conversion of food. The purpose of this study was to determine the impact of sea bass spawning in cage farming on biomass changes and conversion. In addition, production data on biomass and food consumption were collected. There was a significant difference between the sexes in the total length and weight of the veterans in the second year of life, while in the third year there was no difference and this indicates that it is difficult to predict the impact of sex on average size. The GSI in the third year of breeding differed significantly between males and females and should be significantly influenced by sexual fish during weight loss. The difference in VSI at spawning time between males and females is caused by differences in gonad size. The relative size of the gonads in sea bass in cage farming is influenced by sex and size.