Life history invariants

To my knowledge, life history invariants were first made explicit by Ray Beverton and Sidney Holt in the 1950s, both in their studies of fishery management and their work on aging (Beverton and Holt 1957, 1959; Beverton 1992). Life history invariants have been rediscovered many times (and probably will continue to be rediscovered (Roff 1984, 1991)), although Charnov's book (Charnov 1993) will probably help to reduce the frequency of rediscovery. In this context, there often arises confusion between dimensionless parameters and life history invariants. In the context of our work, for example, k/m (or m/k) is a dimen-sionless variable - because both k and m are rates - but they are not necessarily invariants of the life history. However, their ratio is an invariant for relative size at maturity (as explained in the text). In 1994, Beverton gave a series of lectures at laboratories of the National Marine Fisheries Service across the USA. These were recently transcribed and published; they can be found at Lectures1994/. The papers of Essington et a/. (2001) and He and Stewart (2001) provide a very nice generalization of some of the ideas we have discussed, with applications to fisheries (which we discuss in Chapter 6).

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