Roach spawners 271, bream spawners 188 and 91 perch spawners were caught during fishing period carried out within 1997-2001. The aim of the work was to investigate the age, GSI and gonadal maturation in the post-spawning period. The results showed that roach was at age 3-7, bream 4-15, and perch 6-13. GSI values of particular species ranged from 1.23 to 2.85 in roach females, and from 0.8 to 1.6 in males; from 0.81 to 5.62 in bream males and from 0.276 to 0.758 in males; from 1.2 to 5.6 in perch females and from 2.4 to 4.8 in males. Histological observations of gonads showed that roach females start the first spawning at age 3. or partly at 4., while males in the second- third year of life. In case of bream, females start the first spawning in the seventh year of life, whereas males in the sixth year. The spawning time of both fish species started in the Solina reservoir about one month later than in warmer dam reservoires. Perch in the Roznow dam reservoir spawned in April, post spawning gonad regression underwent through a month, and the process of gonad recrudescence started in June. More than 60% females of perch spawned in Roznow, post spawning gonad regression underwent through a month, and the process of the protoplasmatic growth of oocytes started in June, while the trophoplasmatic growth was observed in July, August and in September.

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