Fish Population Dynamic and Stock Assessment

6.5.6 Relative response model

This model was developed by Alagaraja (1984). The aim of this model is that removal of more fish in one year leads to better survival and growth in the residual stock. Increasing the fishing effort leads to increase in catch and when fishing effort goes beyond maximum, the response of the stock continues to be positive but the stock will show sign of depletion. Finally this results to a nil stage (Zero level), negative response of the stock to the fishing effort.

$$Ct + 1 = a + bc_t$$

Ct+1 = catches at successive periods. (Say, years)

Ct catch in a particular year.

The curve is sigmoid type where Ct reaches the asymptotic maximum. The maximum harvestable catch is a/1-b.