Prussian carp Carassius gibelio in the Charvak reservoir of Uzbekistan: morphological and molecular-genetic characteristics

Morphological variability in response to environmental features is an important feature of alien species, increasing their adaptive capabilities and facilitating naturalization in new habitats. The prussian carp Carassius gibelio is currently very widespread in the world. Much of its current range is believed to be acquired as a result of human activity, with the prussian carp recognized as an invasive species capable of having a significant impact on recipient ecosystems. On the territory of Uzbekistan, prussian carp has been known in the lower reaches of the Syr-Darya and Amu-Darya since the 4th millennium BC, and was also recorded in the first half of the 20th century. However, its numbers were not large. In the 1960s, the Amur form of the prussian carp was introduced into the water bodies of Uzbekistan, as a result of a targeted introduction from the "Savvino" fish farm near Moscow and the accidental import of herbivorous fish with juveniles from the Russian Far East, after which its unauthorized resettlement began with planting material of cultivated cyprinids. In the 1970s, prussian carp found their way into the Charvak Reservoir. This is a mountain cold-water reservoir, formed on the Chirchik River (the right tributary of the Syrdarya River) and is located between the spurs of the Western Tien-Shan. With an area of only 37 km2, 2 , it has a volume of about 2 km3 3 and a depth of more than 50 m. The reservoir is characterized by summer drawdown of the water level used for irrigation in the river valley Chirchik. This causes an almost complete absence of vegetation in the water area of the reservoir. Despite the atypical conditions, the prussian carp formed a self-sustaining population. There is none below the reservoir dam to the middle reaches of the Chirchik River. Indicators of counting characteristics of prussian carp in reservoir are D III-IV 17-19; A II 5-6; 26-30 (average 29) scales in the lateral line; on the first gill arch, 40-53 (on average 48) gill rakers and generally correspond to the characteristics in this climatic zone. Indices of plastic characteristics, both in traditional morphological analysis (see Table 1 ) and in the analysis of morphometric distances according to the "truss protocol" assessment method ( see Table 2 ), do not have pronounced differences from the indicators of prussian carp living in a lowland reservoir Tudakul and in the fish ponds of the fish hatchery of the Research Institute of Fisheries of Uzbekistan. Analysis of the nucleotide sequences of the cyt b gene of prussian carp from the Charvak reservoir showed their similarity with samples from the upper reaches of the Yangtze river, China ( see Table 3 ), which proves Far Eastern origin of prussian carp ih the Charvak reservoir. It is likely that it was the prussian carp, brought from the Far East, that ensured the growth in the number of the species in Uzbekistan. The question of the breadth of distribution of the Amur form of prussian carp in the region and the preservation of its native form currently remains open and requires further research using molecular genetic methods.