ON SOME ADAPTATIONS TO THE REGULATION OF 



POPULATION DENSITY IN FISH SPECIES WITH 



DIFFERENT TYPES OF STOCK STRUCTURE 



G. V. Nikol'skii 



Biology and Soils Faculty, Moscow State University and 

 Institute of Animal Morphology, U.S.S.R. Academy of Sciences 



The dynamics of the number and biomass of animal populations is a compU- 

 cated process of adaptive interaction of a population and the changing 

 conditions of its existence: when studying the population dynamics of any 

 organisms the knowledge of the character of adaptive response of a popula- 

 tion to the change of the conditions of Hfe is as necessary as the knowledge 

 of the character of the change of these conditions. Unfortunately, until 

 lately the forms of adaptive response of the population to the changes of the 

 conditions of life have not been paid due attention. 



Only in the two most recent decades have a number of papers connected 

 with this field been pubhshed (Severtsov, 1941; Vasnetsov, 1947; Svardson, 

 1949; Monastyrskii, 1949, 1952; Nikol'skii, 1950, 1953 et al\ Lack, 1954; 

 Naumov, 1955; Beverton & Holt, 1957; Le Cren, 1957; Aim, 1959; et al). 

 These papers were devoted to the analysis of forms of the adaptive response 

 of the populations of different animals to changes in their conditions of life, 

 primarily to changes in food supply at different developmental stages. 

 (Under food supply I mean not only the food available in the basin, but also 

 the conditions necessary for its procuring and assimilation.) 



As far as I know, S. A. Severtsov (1941) was the first to note that the type 

 of dynamics of the stock of a species (i.e. the age composition of the popula- 

 tion, the time of maturity, fecundity, the sex ratio) is characteristic of a 

 species and reflects the character of its adaptations to the environment. 



S. A. Severtsov was right in saying that the population dynamics of a 

 species could be called a focus at which all its peculiarities were reflected; 

 they were the result of all aspects of its ecology (i.e. reproduction, feeding, 

 growth, mortahty) which in turn are determined by the adaptions of the 

 species. The type of stock dynamics, hke the other properties of a species, 

 is developed in the course of speciation. The character of the dynamics of 

 the species population, naturally, can undergo changes within certain limits, 



