Variability of plastic features of size groups of the american catfish Ameiurus nebulosus (Lesueur, 1819) – alien species in the water bodies of Belarus

A scheme for measuring the plastic features of the brown bullhead, including 28 morphometric characteristics, has been proposed. Based on the cluster analysis of morphometric characteristics, the size groups of species of a model water body were determined (Karpin village pond, Maloritsky district, Brest region).The change in the exterior parameters of the brown bullhead during its ontogenesis has been shown for the first time. It is proposed to divide brown bullhead individuals into 3 size groups for analysis: A – young individuals not involved in reproduction (body length without a caudal fin up to 135.0 mm); B – mature individuals that have started breeding (sizes from 136.0 to 174.0 mm); C – adults, actively breeding individuals (sizes from 175.0 to 187.0 mm).