population during the period of the change in generations, can be looked 

 upon as a characteristic reflecting the absolute weight increase of 

 individuals surviving through the year. The rate of growth and natural 

 duration of life of individuals are genetically determined and vary, 

 depending on the environmental conditions, only within limits permitted 

 by the genotype. From this standpoint, P5 is a genetically determined 

 characteristic of the population, resulting from the possibility of its 

 existence under the conditions in question with a mean duration of life 

 determined by the specific genotype and a fraction of individuals 

 surviving through the year determined by the population curve of 

 mortality and, obviously, showing selective preference. 

 Correspondingly, the value of P^ is the minimum of living matter which 

 can be formed during the course of a year, necessary for stable 

 existence of a population of a given age structure. 



Naturally, the value of P^ is always less than the biomass of the 

 population, while the rate of turnover of matter (P^/B coefficient) is 

 related by a rigid, almost linear, inverse dependence to the age of the 

 individuals which predominate in terms of number, and is approximately 

 inversely proportional to the limiting duration of life of individuals 

 of the given population. In populations in which the age of most 

 individuals is < 1 year, the full cycle of living matter occurs in 

 approximately 1 year and P^/B =1. As the duration of life increases, 

 the value of the P^/B coefficient decreases proportionally. In species 

 which form several generations during the course of a year, the 

 supporting production must be correspondly greater than the biomass. 

 Since the mean age of individuals of a given population is determined 

 essentially by genotypic peculiarities of the species and changes 

 slightly during different seasons of the year, the value of the annual 

 P5/B coefficient, calculated for different seasons, fluctuates 

 insignificantly. Therefore, calculation of the mean annual value of 

 this coefficient on the basis of a single sample is rather reliable, 

 regardless of the time it was produced. 



The rate of turnover of growth production of a population (Pg/B 

 coefficient) depends strongly on the relationship of elimination Tn 

 various generations and their relative numbers and changes significantly 

 (sometimes by several times) from season to seaon. The relationship 

 between the growth production of a population and its supporting part 

 depends on the age structure of the population. The greater the 

 relative share of juveniles and individuals of the younger age groups in 

 the population, the greater the Pg:Ps ratio and the greater the 

 prospects for the positive development of the population under these 

 conditions. Actually, young individuals with low biomass have great 

 potential for weight gain, and with a given level of elimination, an 

 increase in their number creates a reserve of reliability for continued 

 existence of the population. 



If the total level of elimination is reduced, particularly in the 

 early, most sensitive phases of postlarval ontogenesis, and the survival 

 rate of individuals is increased (for example, by mariculture) , an 

 increase in growth production should occur, and as time passes, a 

 proportional increase in the number of surviving juveniles should result 



313 



