Reproduction is a link in the life cycle of fish that ensures the existence of the species through reproduction. Fish are characterized by sexual reproduction, although in many species of herring, salmon, carp sex cells, once in the water, develop parthenogenetically, ie without fertilization, but only to the stage of fragmentation, in exceptional cases - until the resorption of the yolk sac (herring, burbot).Fish reproduction is characterized by a number of specific features due to the aquatic way of life.