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the depositing by fish of their reproductive products—mature roe and milt (seminal fluid, ejaculate)—with subsequent fertilization. In most fish, fertilization of the roe is external, occurring outside the body of the female, in water. Fertilization occurs in certain definite places, or spawning grounds, where conditions for development of offspring are favorable. Lithophilous fishes, such as sturgeons and salmon, deposit their roe on rocks. Phytophilous fishes spawn on vegetation and include the carp and the European bream. The roe of pelagophilous fishes, such as the tolstolobik (Hypophthal-michthys molitrix) and the chekhon’ (Pelecus cultratus), undergo development in open water.
Every species of fish is adapted to particular spawning conditions—to a certain water temperature and salinity and to a specific substrate. Many fishes take on a special mating dress. The presence of certain conditions and of individuals of the other sex signal the start of reproduction. In the USSR much work is being done in the study of spawning conditions and in the protection of the spawning grounds of commercial fishes.
REFERENCESNikol’skii, G.V. Ekologiia ryb, 3rd ed. Moscow, 1974.
G. V. NIKOL’SKII