Estimating Parameters in a Flexible Growth Equation, the Richards Fonction

Two methods are presented for estimating parameters in the Richards function, a generalized growth equation. Both methods use typical mark–recapture data: initial and final size separated by a time interval. Three examples are presented. Data on the sea urchin, Diadema setosum, is best fit with Method I and tree seedling (Acer pseudoplatanus) data by Method II. Cisco (Coregonus artedii) growth is described about equally well by either method. The two methods could be applied to population growth in numbers as well as individual growth in size.Key words: Richards function, Brody–Bertalanffy, logistic, growth