Fish of the genus Ameiurus were introduced in Croatian freshwaters in 1905. Knowledge about taxonomy and distribution of the genus Ameiurus in Croatia is scarce. In this investigation it is determined which of the species of the genus Ameiurus is present in Croatia. In the research, 130 fish from 8 carp fisheries were analyzed. 25 morphometric measures were measured and number of fin rays in the dorsal, anal, pectoral and ventral fin were measured. Measurements show that all of them belong to species Ameiurus melas (black bullhead), and not the species Ameiurus nebulosus (brown bullhead) what was assumed. By total and standard body lenght and by body weight, fish were categorized and absolute and relative frequency were determined. Structure of the investigated population of the species Ameiurus melas showes that most fish have total lenght (LT) between 80 and 100 mm and 180 and 200 mm. Most of the fish of the investigated population have a lower body weight, which means that most of them are young individuals. Meristic characteristics, number of fin rays, show that there are no relevant differences in the number of fin rays stated by other authors, but in the anal fin, variation in the number of soft fin rays is noticed. Number of fin rays is presented by a formula. In the statistical analysis of the data, principal component analysis was used. Results show that there are no relevant morfphometric differences between the fish of the investigated populations from different fisheries in Croatia.