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Keywords:

  • fish growth;
  • natural mortality;
  • optimal life history

Abstract

We revisit the empirical equation of Gislason et al. (2010, Fish and Fisheries11:149–158) for predicting natural mortality (M, year−1) of marine fish. We show it to be equivalent to inline image, where L (cm) and K (year−1) are the von Bertalanffy growth equation (VBGE) parameters, and L (cm) is fish length along the growth trajectory within the species. We then interpret K in terms of the VBGE in mass inline image, and show that the previous equation is itself equivalent to a −⅓ power function rule between M and the mass at first reproduction (Wα); this new −⅓ power function emerges directly from the life history that maximizes Darwinian fitness in non-growing populations. We merge this M, Wα power function with other power functions to produce general across-species scaling rules for yearly reproductive allocation, reproductive effort and age at first reproduction in fish. We then suggest a new way to classify habitats (or lifestyles) as to the life histories they should contain, and we contrast our scheme with the widely used Winemiller–Rose fish lifestyle classification.