Zoological Institute, RAS,
199034 St.-Petersburg, Russia
e-mail: model@zin.ru
We consider an ideal population with a stable age composition changing according Lotka equation. Additional assumptions are made concerning the constancy of population size, independence of specific mortality rate on age, and linear dependence of female fecundity on its weight A relationship has been obtained (N[α, ω])/(n0)=(scl0w[α, ω])-1 where n0 is initial numbers of a generation, N[α, ω] is a total number of the mature part of the population, w[α, ω] is a mean weight of a mature individual, s is sex ratio, с is specific fecundity (per unit of weight) and l0 is the probability of larval surviving. The growth of an individual is described by the Bertalanffy function. Methods of calculation of life history parameters are discussed. A method is proposed to calculate the age of maturity (α) and at the end (ω) of the reproduction period as first and second inflection points of the growth rate curve. Based upon data on development of 27 populations of several species of fishes of inland waters of Russia the following relationships have been obtained: (N[α, ω])/(n0)=0.087w[α, ω])0.078 for populations with w[α, ω]<100g, (N[α, ω]) /(n0)=0.037w[α, ω])0.278 for populations with w[α, ω]>100g и (N[α, ω])/(n0)=0.063w[α, ω])0.189 for all populations.
