The growth performance of juvenile sturgeon (Acipenser gueldenstaedtii Brandt & Ratzenburg, 1833) was studied in experimental net cages (2 m x 2 m x 2 m) in freshwater Sapanca Lake. Fertilized eggs were imported from Krasnodar, Russia in January 2001. Two experimental stocking densities were employed (12 and 8 ind. m(-3)). Sturgeon were hand-fed a pelleted commercial trout feed twice daily throughout the 203-day experiment period. Fish were grown at ambient temperature (12.7-28.5degreesC) and natural photoperiod. Initial and final mean body weights were 279.5 g (+/-31.27) and 1112.8 g (+/-234.77) in the first group, and 271.1 g (+/-28.21) and 1140.5 g (+/-213.31) in the second group, respectively. Results were a fourfold biomass density increase in both trials from an initial 3.48 to 12.4 kg m(-3) (high density) and 2.2 to 8.8 kg m(-3) (low density). Mean specific growth rate (SGR) was determined as 2.69% day(-1) in both groups. Mean condition factor (CF) at the end of the experiment was 0.36 +/- 0.05 in the high-density group and 0.41 +/- 0.05 in the low-density group. Mean feed conversion ratio (FCR) was calculated to be 5.7 and 5.8, respectively. Survival was 92.7% in the first group (high density) and 96.1% in the second group (low density). The results demonstrated that sturgeon juveniles can be raised in cages and that growth performance (CF, SGR and FCR) and mortality of sturgeon were not significantly different at the two stocking densities (P > 0.05) tested.