The FishBase graphs of natural mortality are based on what is surely the largest compilation of independently derived natural mortality estimates of fish in the world, i.e., similar, but independent data do not exist which could be used to verify the generalizations derived from this dataset. Thus, since independent replication of our results is difficult, we must be very careful in presenting generalizations based on this dataset.

Here, we have therefore limited ourselves to two graphs testing earlier generalizations of Beverton and Holt (1959) and Pauly (1980). The first of these graphs (Fig. 27) is a plot of logM *vs.* logK, the curvature parameters of the von Bertalanffy growth function. As might be seen, this confirms that K, which is related to longevity, is a good predictor of M. The variance is high, however, suggesting that other factors also influence M.

Our second graph (Fig. 28) documents two of the factors influencing M, size and environmental temperature. The dots are estimates of logM *vs.* the corresponding estimates of logL¥
_{,} with open dots for estimates from waters below 20°
C (about 2/3 of all cases), and full dots for the rest, referring to tropical fishes.

As might be seen, M is not only related to L¥
(and to K; see Fig. 27), but also to temperature, notwithstanding Charnov (1993), whose concepts of ‘Beverton and Holt invariants’, of which M/K is supposed to be one, do not allow for the temperature effect so evident in the data at hand.

**References**

Beverton, R.J.H. and S.J. Holt. 1959. A review of the lifespans and mortality rates of fish in nature and their relation to growth and other physiological characteristics, p. 142-180. *In* G.E.W. Wolstenholme and M. O’Connor (eds.) CIBA Foundation Colloquia on Ageing: the lifespan of animals. Vol 5, J. & A. Churchill Ltd., London.

Charnov, E. 1993.** **Life-history invariants: some explorations of symmetry in evolutionary ecology. Ecology and Evolution. Oxford University Press, Oxford. 128 p.

Pauly, D. 1980. On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. J. Cons. CIEM 39(2):175-192.

**Daniel Pauly**