Fish Population Dynamic and Stock Assessment

4.4.1. Exploitation ratio

The exploitation ratio is defined as the fraction of a year class recruits that is caught during all the year of existence (Ricker, 1975).

If M and F are available, exploitation ratio (E) could be calculated.

E = $$F\over {F+M}$$

This allows assessing whether the stock is overfished or not. According to Pauly (1983), on the assumption that optimal value of Eopt is almost equal to 0.5. According to Gulland the use of E $$\approx$$ 0.5 as optimal value for exploitation ratio itself resting on the assumption that sustainable yield is optimized when F $$\approx$$ M.