A model experiment to analyze the accuracy of estimation of 

 production by this method has shown that the determination of the mean 

 annual growth production of a population based on a single sample is 

 rather reliable and accurate, if the time of collection of the materials 

 is adjusted approximately to the middle of the period of supplementation 

 of the population with juveniles (Golikov, Menshutkin, 1971). In 

 temperate waters in the northern hemisphere, this is usually observed in 

 the summer or early fall. This conclusion has been confirmed by 

 analysis of seasonal changes in the production process of a number of 

 species of gastropoda, differing in their biogeographic distribution and 

 duration of life (Golikov, Menshutkin, 1973; Golikov, 1975b). 



In cases when observation of the structure of a population is 

 performed at a time which is not favorable for determination of the 

 annual growth production (peak of supplementation with juveniles or 

 maximum of elimination), the growth production calculated up to this 

 time may differ greatly from the mean annual growth production (by up to 

 80%). However, 2 samples, taken at an interval of approximately 1/2 

 year, allows the possible error to be decreased to less than 25%, while 

 4 observations during the various seasons of the year allow the mean 

 annual growth production of a population to be estimated with an error 

 of less than 5% (Golikov, Menshutkin, 1971). If it is possible to 

 observe the structure of a population during various seasons of the 

 year, the mean annual growth production can be defined as the mean of 

 the annual productions calculated for each moment of observation (Pg,-): 



n 



•^1 Pgi 

 p„ =IiL_lL (4.5) 



•^gm n 



where n is the number of observations. 



Obviously, of greatest interest is observation of the full 

 production of a population, including all living matter produced during 

 the course of a year. The total production of a population must include 

 all of the juveniles produced during a year. The total production of a 

 population can be approximated, depending on the nature of elimination, 

 by one of the following two equations: 



" 1 1 



P = NqWo +Jq^ (N^ + Nx+l) (Wx+1 - W^) ^ (4.6) 



or 



P = NqWo +Jq N, (W,+i - W,) ^ . (4.7) 



where NqWq is the biomass of individuals of a given year of birth. 



311 



