Their task is to understand how successful the natural reproduction of semi—aquatic and riverine fish species is in the shallow-water coolwater zone. And the first results already give reason for cautious optimism.
The warm winter and early warming of the water to spawning values allowed the pike to start spawning in the second decade of March. Today, this is bearing fruit: juvenile pike are found in almost every litter of juvenile sledge. The Kultuchnaya zone is a special place: in summer it becomes a real dining room for the younger generation of fish. Here they find food for roach, bream, catfish, carp, pike, tench, walleye and many others.
Now, in June, the concentrations of juveniles have not yet reached their peak: most of them have not yet begun to roll massively into the forage—rich areas of the kultuchnaya zone and further into the Northern Caspian. Juveniles stay at depths from 0.3 to 1.5 m, hiding and gaining strength among thickets of cattails, reeds, rushes, hedgehogs, pods and water lilies. Scientists record especially dense accumulations in shallow waters with sparse thickets at depths of 40-90 cm, where the concentration reaches 14-31 specimens/m2. In deeper areas (100-150 cm), juveniles are noticeably smaller — only 3-8 specimens/m2.
Among the caught juveniles are roach, bream, gaster, rapeseed, ide, crucian carp, carp, pike and rudd. At the same time, in recent years, scientists have noted one important trend: the number of so—called low-value species is growing - crucian carp, bleak, gobies, pluckers, rudd, bittern. The reason lies in the peculiarities of the current period: the level of the Caspian Sea has dropped to a critically low level — 29.14 m, and the low‑water regime resembles the situation of the 70s of the last century, when the yield of these species also increased markedly.
The regime of water releases from the Volga hydroelectric power station plays a huge role in the fate of juveniles. If they are long enough and stable in summer, this will help the juveniles to successfully roll down and gain weight in the shallow estuarine coast of the Volga and in the desalinated part of the Northern Caspian Sea. Scientists will continue to monitor fish migrations and natural reproduction throughout the summer, and preliminary results will traditionally be presented in November.
VNIRO Press Service
