ЕСТЕСТВЕННОЕ ВОСПРОИЗВОДСТВО СЕРЕБРЯНОГО КАРАСЯ CARASSIUS AURATUS GIBELIO (BLOCH, 1782) В НИЗОВЬЯХ Р. ВОЛГИ В 2012-2013 ГГ

Abstract

Observation of spawning of carp sires and fattening of larvae and fry in 2012-2013 was carried out by the staff of the Laboratory of Fish Reproduction Federal state scientific institution "CaspNIRKh" from April to July on the spring floods in the lower reaches to the Volga river, in the west part: in Gandurinski, Chief, Kirov banks; in the east: in Belinsky and Vasilevsky banks, using research vessels and cars. The studies took place on the spawning grounds of the lower reaches of the Volga. Estimation of carp juvenile abundance was conducted according to the results of registration survey of juveniles in the hollow period of flood water on the spawning grounds of the western and eastern parts of the Delta. Depending on the area of the studied reservoir there were selected at least 5 samples at different sites. The catch of carp juveniles was carried out with a 6-meter scraper made of sprat net with a rare gas bag. Hydrological parameters were provided by the researchers of the Laboratory of water problems and toxicology, Federal state scientific institution "CaspNIRKh". The reliable research data assert that more favourable conditions for crucian carp breeding were formed in 2013. The duration of flooding and spawning had a positive impact on the natural reproduction of carp. Low water level in the delta front and overgrowing of water bodies in recent years contribute to creation of favorable conditions for silver carp spawning, survival of juveniles, availability of food and increase in their number. In high water year of 2013 average weight and length of juveniles was higher in all locations, compared to 2012. In 2013 in all the spawning grounds under study a large proportion of crucian carp juveniles (84.09%) was characterized by viability (F and G stages), whereas in 2012 in the spring floods of the upper zone of the eastern part of the Volga the early larvae of stage C were registered. In 2013 on the spawning grounds of the Delta the average concentration of juveniles of crucian (33.4 thousand sp/ha) and abundance of juvenile carp were higher, compared to 2012 (2.1 and 2.6 times, accordingly).