The generation fecundity of roach in 1985-1990 and its population fecundity in 1987-1992 were determined in the coastal lakes Gardno and Łebsko in the Słowiński National Park. The number of specimens which attained recruitment age annually per mature female was also determined. The average fecundity of the same generations from the two reservoirs was similar at 4.1·109 eggs in Lake Gardno and 4.4·109 in Lake Łebsko. The most abundant generation of females was observed in 1985; it was also the most fecund producing 7·109 eggs in Lake Gardno and 5.3·109 in Lake Łebsko. The subsequent generations were less numerous and produced fewer eggs. The four and five year old females in Lake Gardno had the highest egg production in each of the analyzed years. The most fecund females in Lake Łebsko consisted of specimens which were five and six years old. In the 1987-1992 study period, the average fecundity of the spawning roach populations in Lake Gardno was 7.4·109 eggs and in Lake Łebsko it was 5.9·109. From eight to 14 specimens of both sexes at recruitment age (age group 2+) were reported per mature female annually.

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