Fish Population Dynamic and Stock Assessment

6.1.4. Procedure

(i) Collect data on yield of a stock.

(ii) Collect effort data (Number of standard vessels) employed to catch the stock in question.

Collect these two data for a number of years. For Schaefer model, effort f(i) is taken as X and Y(i)/f(i) (catch per unit effort) is taken as Y.

For Fox model, effort f(i) is taken as X and ln [Y(i) / f(i)] is taken as Y variable.

In Schaefer model,

MSY = - 0.25 . $$a^2$$/ b

FMSY = - 0.5 * a / b

In Fox model,

MSY = - (1 / d ) * Exp. (c-1).

FMSY = - 1 / d.

(Note : The constants ‘a’ and ‘b’ for Schaefer model should be replaced by ‘c’ and ‘d’ in Fox model)