Estimating Survival Rate (S) - Powell Method

There are a number of methods to estimate survival rate (S) of a fish population, such as CPUE, Heincke (1913), Jackson (1939), Beverton-Holt (1956) and Ricker (1975). Powell (1979) wrote this method in case that there are no biological data anything but lengths exist.

From a Beverton-Holt equation L_inf = - a/b and Z/K = -(1+b)/b, where a is y intercept, b is slope, Z is instantaneous coefficient of total mortality, K is growth coefficient. Lengths on the table (left) are mean lengths. a = 11.906 and b - - 0.2349 (R square = 1.0) after regression on SPSS. Thereby, L_inf = 50.69 cm, Z/K = 3.26, and if K value is known, S can be calculated by equation S = exp (-Z).












revised on Apr. 3 2007
by Yeongha Jung