where N is the number of age groups. At is the time sector analyzed. 



Considering that in a stable population (one in which upon 

 completion of a generative cycle, the initial dimension-age structure 

 and population are restored) of multiannual benthos organisms, the 

 annual production (P) is equal to elimination (E), production can be 

 estimated by the equation: 



P = E = I ^ (W, + W,+i) (N, - N^i) -^ , (4.3) 



T=0 



reflecting the mean weight of individuals eliminated from the population 

 over the time of observation. To determine the annual production, the 

 results of observations for individual sections of time are added. 



Obviously, the accuracy of calculation of production will be 

 higher, the more frequently observations are performed. This results 

 from the need for the most accurate possible determination of the time 

 of elimination of individuals in various age groups and the appearance 

 of replacements in the new generation or by migration. If the sampling 

 frequency is too low, the weight gain of individuals which disappeared 

 from the population long before the moment of observation may be 

 included in production, leading to an elevated calculated value of 

 production or, conversely, lack of data on the time of supplementation 

 of a population will lead to reduced values. Naturally, one must be 

 sure that the calculation of production is performed for the same 

 population studied at the beginning of observations. 



Considering the methodologic difficulties, a number of authors have 

 suggested that the daily growth of individuals or specific P/B 

 coefficients of populations obtained experimentally or by mathematical 

 calculation be used to calculate production (Konstantinov, 1967, 1970; 

 Zaika, Malovitskaya, 1967; Greze, 1967, 1973a, b; Mathews, 1970; Zaika, 

 1972; Burke, Man, 1974). However, it is obvious that the P/B 

 coefficients or cumulative daily growth of individuals in different 

 generations depend greatly on the relationship of the populations of 

 individuals of different ages and the conditions of existence of 

 populations and, consequently, are essentially different during 

 different seasons of the year and in populations living under different 

 conditions. This once more emphasizes the need to take samples as 

 frequently as possible in order to allow estimation of changes in 

 population and the weight of individuals in various cohorts. 



Calculation of the production of populations of benthic animals can 

 also be performed on the basis of the ecologic-physiologic approach to 

 estimation of the weight increase of individuals, which is dependent on 

 the intensity of their metabolism. The production is calculated on the 

 basis of the ratio of the growth of individuals to the cost of 

 metabolism, which is expressed by the equation for the coefficient of 

 net production, or the effectiveness of utilization of assimilated food 

 for growth: K2 = P:(P + R), where P is the production (cal), R 

 represents the cost of metabolism (Winberg, 1966, 1968; Bedman et al., 



308 



