The weighted F described above for illustrating trends is not comparable to the Fs used as biological reference points for management such as F max (Beverton and Holt, 1957) and F 0.1 (Gulland and Boerema, 1973).
The latter are usually the fullyrecruited F (Northwest Atlantic) or are representative of the unweighted average F over
some selected age range encompassing the last of the partially recruited age groups and the first of the fully recruited age groups (Northeast Atlantic).
Thus, the way of calculating reference points varied among stocks and, indeed, sometimes for the same
stock over time.