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The aim of this study was to investigate changes in reproductive success including fertilization and hatching rates and larval performance as indicated by body weight and resistance to osmotic stress in captive common barbel (Barbus barbus L.) throughout the reproductive season. Spawning of B. barbus broodstock in captivity proceeded from February 01 to June 21 during 2006. Within the spawning period, fertilization and hatching rates and larval performance (body weight and resistance to osmotic stress) were studied at 7-day intervals. The average number of spawnings for each female was 2.8. Average fecundity was 1650 ± 460 eggs per spawning. A high proportion of females delivered poor egg quality (overripe eggs) during the spawning season from 57% on February 15 to 38% on May 31. The lowest fertilization and hatching rates were observed at the beginning (February 1, 18.5 ± 2.5% and 5 ± 2.5%, respectively) and the end (June 21, 25 ± 7% and 5.5 ± 2.5%, respectively) of the spawning period. While the highest values of both rates were found in period from March 22 (72.5 ± 5%) to May 10 (68 ± 4%) and from April 19 (53.8 ± 10%) to May 17 (50.5 ± 5%), respectively. The lowest larval body weight and resistance to osmotic stress were found at the beginning (8.0 ± 0.7 mg and 0 ± 0%, respectively) and the end of the spawning period (8.0 ± 0.7 mg and 25.2 ± 5%, respectively). The highest larval body weight and resistance to osmotic stress were recorded from March 15 (11.3 ± 0.9 mg) to May 31 (11.0 ± 0.7 mg) and from May 10 (93.5 ± 5%) to May 31 (90.7 ± 8%), respectively.

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