Abstract
In July and August 2010, the Lincoln-Petersen capture-recapture method was used to assess the size and basic structure of a newly established population of the endangered in Poland cyprinid fish lake minnow, Eupallasella percnurus (Pall). The population that inhabits a small (0.08 ha) peat excavation site in the village of Kowalicha near Radzymin (Mazowieckie Voivodeship, Poland) was initiated in 2004-2006 using the translocations of a total of 1530 cultivated individuals, mostly juveniles aged 0+. The total size of the E. percnurus population was estimated to be 600 individuals excluding aged 0+. The population size is not considered to be large in comparison with other populations inhabiting water bodies of similar surface areas. Males proved to be predominated by females - phenomenon typical of populations of this species - but at relatively high ratio of approximately 1:4. Most of females were aged 2+, whereas most of males were older (3+). These data indicate that the population remains in the early stages of development. The Lincoln-Petersen method proved useful in the studies of the size and structure of E. percnurus populations.