Maria Kosior and Tomasz Wandzel
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: Baltic Sea, Szczecin Lagoon, Vistula Lagoon, Curonian Lagoon, pikeperch (Stizostedion lucioperca [L.]), absolute fecundity, relative fecundity, length at sexual maturation

Abstract.
This paper presents the results of pikeperch fecundity estimates made using materials collected in the pre-spawning season of 2000. Pairs of ovaries were collected from fish inhabiting the Polish zones of the Szczecin and Vistula lagoons and the Russian zone of the Curonian Lagoon.
It was confirmed that the dependencies of absolute fecundity on age, length and gutted weight of fish which reproduce in the Szczecin Lagoon and the Vistula Lagoon are similar, but they vary significantly in those which reproduce in the Curonian Lagoon. The corresponding increases of absolute fecundity with total length and weight were the slowest in the Curonian Lagoon females. The relative fecundity of females from the Szczecin and Vistula lagoons increased along with total length, gutted weight and age. In the Curonian Lagoon, a dependence between relative fecundity and length and age was not confirmed, but as weight increased, relative fecundity decreased. Length at sexual maturation was determined based on the smallest females caught which had gonads in maturity stage IV on the Maier scale; in the Szczecin and Vistula lagoons it was 36 cm and 42 cm, respectively. After reaching a length of 42.9 cm, 50% of the females in the Szczecin Lagoon began to reproduce; in the Vistula Lagoon this figure was 43.9 cm.