Mortality (Fishing F)

Fishing mortality F is the instantaneous rate at which fish die from fishing, the one term of total mortality that managers control directly. It is the F in Z = M + F and is roughly proportional to fishing effort through catchability, q, so F equals q times effort. Reference points cast it as the lever of management: F is held at or below F_MSY to deliver maximum sustainable yield, and cut below F_MSY to rebuild a depleted stock. An F above F_lim, the limit point, risks recruitment overfishing. Total allowable catch and effort controls are the instruments that pin F to its target.