The degree of maturity of the gonads is also characterized by maturity coefficient and maturity index. The maturity coefficient is the ratio of gonads weight to fish body weight (in %). In fish with spring-summer spawning (carp, pikeperch, roach, etc.), the maturity coefficient is highest in spring, decreases in summer, and begins to increase again in the fall. Fish with fall-winter spawning (salmon) have the highest maturity factor in the fall.

Gonad maturity index - the percentage ratio of the gonad maturity index calculated in separate periods of their maturation to the maximum maturity index.