Critical periods in the development of fishes

A concept of the critical periods in the development of fish is developed. It is wrong to identify the critical periods in development with periods of heightened sensitivity. Certain moments in early ontogeny, when embryos and larvae with morphological and physiological deficiencies inherited from the parents or acquired during embryonic and early postembryonic development under the influence of unfavorable environmental conditions arrive at a degree of differentiation which prevents their further development and existence, are the critical periods in development. Numerous data are presented on critical periods of development during the larval life of fishes from different families in support of the concept developed.