Treacherous, mysterious alien. Crucian
The reasons for this confusion and uncertainty among amateur fishers should be explained by a number of unusual circumstances and conditions. Firstly, in the popular literature on sporting and recreational fishing, two varieties of crucian carp are traditionally described – gold and silver. Moreover, different authors have their own name for silver carp: silver, white, silver (oblong). However, when comparing, it is easy to see that even in appearance (size, shape, weight), the new “brother” is significantly different from its classical form. Secondly, if the well-known crucian predominantly lives in ponds, lakes, small rivers with a small current, then its new variety lives in the Volga, Akhtuba and the Don, in which the current velocity is quite noticeable. Thirdly, common crucian carp is caught from May to September-October, and even in some regions in winter, while the Volga and Don alien only in strictly defined periods of 2-3 weeks. Fourth, the average weight of ordinary goldfish ranges from 200-300 grams, reaching a maximum of 1 kg, and its “cousin” for the most part weighs from 1 to 2.5 kg. Fifthly, when studying fishing literature and from oral stories, Volgograd fishermen are surprised to learn that in the middle and upper reaches of the Volga, local fishermen have not yet met him (see, for example, “A Successful Fisherman.” Edited by P.V. Ivneva. Gorky, 1986; Yu.K. Yusupov. “On the Volga dawns.” Saratov, 1993). In the light of these factors, the existing leapfrog in the names of silver crucian carp and its difficult to explain, mysterious habits becomes understandable.
Therefore, there is a need to consider in more detail and thoroughly the issue of the differences between the two subspecies of silver crucian carp. Silver crucian Carassius auratus within the range forms a number of subspecies; in the territory of the former USSR, only one subspecies of Carassius auratus gibelio (Bloch) lives. The characteristic and distinctive features of this subspecies are the following: denticles on the last unbranched ray of the anal fin (about 10-15); branchial stamens – 35-49; scales in the lateral line – 28–32; the peritoneum is usually black.
Its initial habitats are the basins of the Amur River and a number of Siberian rivers. The resettlement of Amur silver carp in Europe began in the second half of the nineteenth century. But the mass distribution of the Amur inhabitant occurred in the 30s of our century, when this species began to be bred in ponds as an object of industrial fish farming. Due to its high productivity (annual growth in the 2nd year of life – 125 g, in the 3rd – 250 g, in the 4th – 240 g) and unpretentiousness to the food base, silver crucian carp is placed in artificial reservoirs, and sometimes in natural, in Ukraine, southern Russia, Belarus and Kazakhstan. Acclimatization of the Amur settler was successful.
On the Lower Volga, silver carp began to be found in single copies as far back as the 40s in the river delta. In the 1950s, its abundance abundance increased, and after 20 years the population reached its fishing abundance (in 1979, its catch amounted to 520 tons). In Tsimlyansk reservoir, in carp statistics, crucian carp began to be counted from the mid-80s, when its catches on average began to equal 100 tons.
How, how did the crucian carp migrate from the ponds to the rivers? During large floods, from dams of fish farms, destruction and erosion of dams occurred, and crucian carp rushed to Akhtuba, Don, and Volga in large numbers. Thus, according to the observations of Volgograd ichthyologists, a sharp increase in the number of silver crucian carp was noted over the course of 1-2 km along the course of Akhtuba from the pond drain.
The “outbreak” of the number of silver crucian carp was initially observed in the Lower Don in the years 60-70. In 1986, large herds were at the dam Tsimlyanskaya hydroelectric station. Due to the negligence and carelessness of the fish-lift workers, he was “thrown” into the reservoir, from which he independently mastered the waters of the Middle Don and the Volga-Don Canal. An approximately similar pattern of the distribution of silver crucian carp was observed on the Volga. But so far he has not succeeded in overcoming the dam of the Volga Hydroelectric Power Station and moving to the Volgograd Reservoir and above.
Compared to indigenous species of fish, crucian carp found its advantages: unpretentiousness to the oxygen regime, a wide hydrological range of habitat (river, lake, pond, reservoir), omnivorous, portioned spawning. The latter factor allows much larger offspring to develop and survive compared to other fish species. His caviar does not ripen immediately and simultaneously, but gradually – in the gonads there are 3-4 different sized caviar groups. In process of maturing and readiness each group of caviar is thrown out by “portion”. After a while, the first follows the second, then the third, etc. during May-July.
Why is the active zhor of silver crucian only in the second half of May or the first days of June, and then its complete extinction sets in?