The perch, a species present in most Polish freshwater reservoirs, is not protected. A continuous decline of the perch population abundance in Poland, reflected in catches of fishermen and anglers over the second half of the last century and in the first years of the 21st century, is mainly a result of increased intensity of fishing. At present, the perch abundance is much lower than that required by sustainable functioning of aquatic communities in which the species diversity and abundance of fish is kept at a stable level corresponding to the trophic status of an area. The aim of the analysis presented was to asses the size and fecundity of perch females at age of maturity and to use the results to propose a protective size which, when deemed legally binding, would contribute to a faster recovery of overfished perch populations without drastic restrictions to fisheries. Materials for the study were collected from the Polish coastal lakes on the southern Baltic coast, from the Vistula Lagoon, from Mazurian lakes in the vicinity of Olsztyn, and from the power station-heated lakes near Konin. Samples were collected in 2000–2005 from catches effected with trap and drag nets; sampling was conducted in late autumn, when the perch growth is arrested, as well as in winter and spring, prior to and during spawning. The smallest females which were ready to spawn had survived three growth seasons (age group 2+) and measured 14.1–16.0 cm total length (L.t.). They contributed 25%to all the females of that age group caught by fishermen. The largest 3-year-old females (22.1–24.0 cm L.t.) occurred sporadically in the catches. The most frequent females at age of first maturity measured about 17.5 cm L.t.Absolute fecundity of the smallest females that spawned for the first time was 5–10 thou. eggs per fish.Afemale measuring 17.5 cm L.t. at age of first maturity carried about 13 thou. eggs. A protective size of 18.0 cm L.t. is sufficient for spawning of 70% of the perch females that have reached maturity for the first time.

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