The morphometric characteristics of the most common commercial fish were studied: carp – Cyprinus carpio L., pike – Esox lucius L., crucian carp– Carassius auratus gibelio Bloch. and perch – Perca fluviatilis L., two years old, with an average mass of 290–330 g., 300–350 g., 150–230 g. and 170–230 g. respectively, caught from the small rivers of the Western Podillia (Strypa, Seret, Zolota Lypa). It was found, that the indicators of full length, standard length, head length, head height at the back of the head, the largest and smallest body height in carp, crucian carp and perch decreased linearly in a number of rivers Strypa – Seret – Zolota Lypa. It is noted, that the values of the liver index in the investigated fish species differ significantly from the representatives of the rivers Seret and Zolota Lypa compared to the species from the Strip River. This indicator increases in the Strypa – Seret – Zolota Lypa range, except for the pike index, which is of the lowest importance in the representatives of the Seret River. All the fish species studied saw an increase in the gills index in a number of Strypa – Seret – Zolota Lypa rivers.
The study demonstrated that the values of the Fulton and Clark fattening coefficients in carp, crucian carp and perch decreased in a number of Strypa – Seret – Zolota Lypa rivers. In pike the highest values of fattening coefficients were noted for fish from the river Seret. Considering the same age of the fish and relatively the same trophic conditions in the studied rivers, it can be assumed, that the differences in morphometric indices are due to different anthropogenic influence on the watercourses. In this case, the least favorable environmental conditions are in the Zolota Lypa river, which is obviously due to its complex pollution.
Predator community and resource use jointly modulate the inducible defense response in body height of crucian carp
