Dominance and occurrence constancy of the fish species in the lower Płonia River

The fish fauna of the lower Plonia River, above and below, the discharge point of the partly treated manure from the Pig Farm at Kolbacz-was surveyed in the years of 1992-1994. Electrofishing conducted four times on the same sections of the river yielded a total of 5 773 fishes, representing 21 species. The fishes belonged to 8 families and they were assigned to four feeding guilds. The highest occurrence constancy index (100%) was observed in roach, perch, and pike. The above species represented also the highest dominance index (67.71, 14.77, and 4.07% respectively).