Fish Population Dynamic and Stock Assessment

6.4.2.2. Ricker equation

To estimate MSY, the equation of Ricker could be used

MSY=$${r_m*\overline{B\infty}}\over4$$...............................................(3)

B$$\infty$$= carrying capacity of the environment for a given stock (This is assumed to

be corresponding to Bv, the Virgin stock size).

‘rm’ = “ Intrinsic rate of increase ” of the population

[‘rm’ could be computed using the equation of Blueweiss et. al. (1978).]

rm = 0.025 * W ^{- 0.26} ……………………………………. (4)

rm = expressed in daily basis

w = is the mean weight ( in g.) of the adult animals under consideration.

Combining the above two equations (Ricker and Bluewiess et. al 1978) and converting to the year as a time unit the following equation may be written.

MSY = 2.3 * W ^{- 0.26} *B_v …………………………………… (5)

This equation can be used to estimate potential yields when virgin stock size and mean weight (in g) of the adult in that stock are known.