Of the 63 species of fish found in the water bodies and watercourses of Belarus, many (all cyprinids, catfish) are thermophilic.
Of the 63 species of fish found in the water bodies and watercourses of Belarus, many (all cyprinids, catfish) are thermophilic. During evolution, they have adapted to living in conditions of significant water temperature fluctuations (from 2 to 25°C). At low temperatures, their metabolism slows down, and their motor activity and feeding decrease or cease. Before wintering, fat reserves accumulate in the fish's body, which are consumed during the winter period.
Different fish species overwinter this difficult period differently. Thermophilic species, such as bream, carp, and tench, gather in huge schools as early as October-November and go into winter dormancy. Individuals of the same species and age winter together. The fish huddle close to each other, and the cold becomes less frightening.
For wintering, fish usually choose deep sections of water bodies with still water or weak flow – so-called wintering pits. These are not necessarily pits in the literal sense of the word; often, they can be flat bottom sections. Fish use the same wintering pits year after year. They are only changed in artificial reservoirs with unstable levels (reservoirs, ponds).
To prevent mass fish catches during the wintering period, the Rules for Fishery Management and Fishing provide for protective measures: commercial fishing of all fish species in wintering pits is prohibited from October 1 to April 15. The list of wintering pits, indicating their boundaries, is specified in the fishery and biological justifications for water bodies.
To preserve the population of the wels catfish, which becomes easy prey during the winter period, a ban on its catch is established throughout the republic from November 1 to March 31. The ban applies to both commercial and recreational fishing.
There are also fish for which cold weather is not a burden at all. Representatives of the salmon family, which include the Chud whitefish and the European vendace, begin their spawning period in late autumn. In this regard, fishing for Chud whitefish is prohibited from November 1 to December 15, and for European vendace from November 15 to December 20.
The burbot, the only freshwater representative of the cod family, also welcomes the cold weather. Warm water depresses it: in summer, at water temperatures above 15°C, the burbot stops feeding and, hiding in bank burrows, under large stones or snags, falls into hibernation. Only in autumn, when the water in the rivers cools noticeably, does the burbot awaken and begin to feed. A spawning ban on catching burbot is established in Belarus from December 25 to February 28.