Climate warming and immigration of a new dominant mollusca Dreissena bugensis
can potentially lead to changing the breeding capacity of benthos feeder fish
species, which live in Upper-Volga Reservoirs. The age of maturation, the
structure of the spawning population, and fecundity are the main indicators of
breeding. Along with the survival rate of hatchling and fishing pressure ratio,
these indicators determine relative species abundance in fish fauna. The purpose
of our work is to study the size and age of maturation beginning and fecundity
dynamics of Rutilus rutilus in the Volga Channel, Rybinsk Reservoir. We
determined individual absolute fecundity by counting eggs in fresh gonads
sub-samples without using fixation. We determined the age of fish by scales, and
we used vertebrae and operculum as additional factors. The performance indicated
that the maturation beginning of females roach occurs at the age of 3+ and
length of more than 9 cm. Late maturing females were at the age of 4+ and length
of more than 18 cm. The beginning of male maturation could not be determined.
The smallest caught males were 7-8 cm and already mature. The fish age limit
reached 12+ years with a length of less than 32 cm. Individual absolute
fecundity ranged from 1.75 to 178.46 thousand. The relative fecundity ranged
from 79 to 308 eggs/g, and an average was 171. The performance concludes that
the high absolute and relative fecundity, and the absence of dynamic pattern in
the conditions of increasing yearly average temperature of the water and
improving the food supply after immigrating Dreissena bugensis, can demonstrate
achieving the limit kind of the breeding capacity of roach.
