The number of eggs hatched by a female of a given species during her lifetime is calculated as the product of the individual fecundity of the fish and the number of spawnings in her lifetime.

Bony fish have the highest fecundity of fish that lay pelagic eggs (moonfish up to 300 million, molva about 60 million, cod 9-10 million eggs). Fish that guard or hide their eggs tend to have low fecundity. Fish that care for their offspring usually have low fecundity. The fecundity of marine fish is usually slightly higher than that of freshwater and anadromous fish.