Comparison of growth performance and biometric relationships in two reciprocal sturgeon hybrids reared in net cages (Sicily, Mediterranean)

This study was designed to investigate growth performance in two sturgeon hybrids reared in two quadrangular £oating cages moored in an arti¢cial pond, representing the ¢rst experience of sturgeon culture performed at Southern Mediterranean latitudes. The research was carried out from December 2000 to July 2001 and tested the growth performance, feeding parameters and biometric relationships. The sturgeons were randomly collected from the cages on a monthly basis, and total length, standard length (SL) and wet weight (WW) were recorded. The speci¢c daily growth rate (SGRW) as somatic WW, food conversion ratio and condition factor (CF) were calculated. Biometric relationships, as linear regression, were also calculated on SL andWWdata. Both hybrids grew slowly from December toApril, but faster during the warm months. The growth performance of the two hybrids seems to be in£uenced by variability of the environmental conditions and, for both ¢sh groups, there was a strong correlation between water temperature and SGRW at temperatures below 25 1C. The CF (constantly below 1) was similar for both hybrids. The regression analysis for WW and SL calculated for the entire period showed a positive allometry for both hybrids, indicating that the ¢shes grew in weight at a greater rate than required to maintain constant body proportion.