Zusammenfassung: Akamine's (1986) BASIC program by Marquardt's method was rewritten for Richards model and its expanded model by the periodic function. For 0.9 similar to 1.1 the “LOG” function is corrected by Taylor series. Data estimated to be negative are cut off. AIC judges the effect of adding n to the parameters. Richards model is not so important in practice but it is important theoretically.

Zusammenfassung: Computer simulation of fish growth was conducted in order to clarify the mechanism of individual variation in terms of coefficient of variation (CV) and skewness of frequency distribution (sk). Normal distributions of initial body length, specific growth rate (growth coefficient) and asymptotic value were supposed. In exponential growth accompanied by the changes of distribution of body length from normal to lognormal, both CV and sk continuously increased.

Zusammenfassung: The growth curves of von Bertalanffy, logistic and Gompertz models were expanded using a periodic function, f (t + 1) = f (t). Each model was expanded into l = l infinity (1-exph sub(1)), l = l infinity /(1 + exph sub(1)) and l = l infinity exp(-exph sub(1)) where h sub(1) = -K(F(t)-F(t sub(0))), F' = f, f = (1 + a)/2 + (1-a)/2 multiplied by cos 2 pi (t-t sub(1)) : a less than or equal to f less than or equal to 1. BASIC programs for each model were written by Marquardt's method. The following subjects were also considered : an expansion into another type, a parameter-error analysis, a comparison with the original model and with Walford's graphical method, and a calculation to determine the extreme points of the growth rate. This expansion of the growth curves is useful and the programs are easily applied to other curves.