A Dynamic Energy Budget model based on partitioning of net production

We formulate a Dynamic Energy Budget (DEB) model for the growth and reprodu ction of individual organisms based on partitioning of net production (i.e. energy acquisition rate minus maintenance rate) between growth and energy reserves. Reproduction uses energy from reserves. The model describes both feeding and non-feeding stages, and hence is applicable to embryos (which n either feed nor reproduce), juveniles (which feed but do not reproduce), an d adults (which commonly both feed and reproduce). Embryonic growth can hav e two forms depending on the assumptions for acquisition of energy from yol k. By default, when the energy acquisition rate exceeds the maintenance rat e, a fixed proportion of the resulting net production is spent on growth (i ncrease in structural biomass), and the remaining portion is channelled to the reserves. Feeding organisms, however, modulate their allocation of net production energy in response to their total energy content (energy in the reserves plus energy bounded to structural biomass). In variable food envir onment an organism alternates between periods of growth, no-growth, and bal anced-growth. In the latter case the organism adopts an allocation strategy that keeps its total energy constant. Under constant environmental conditi ons, the growth of a juvenile is always of von Bertalanffy type. Depending on the values of model parameters there are two long-time possibilities for adults: (a) von Bertalanffy growth accompanied by reproduction at a rate t hat approaches zero as the organism approaches asymptotic size, or (b) abru pt cessation of growth at some finite time, following which, the rate of re production is constant. We illustrate the model's applicability in life his tory theory by studying the optimum values of the energy allocation paramet ers for constant environment and for each of the dynamic regimes described above.