  We synthesise traditional unstructured food webs, allometric body size
scaling, trait-based modelling, and physiologically structured modelling to
provide a novel and ecologically relevant tool for size-structured food webs.
The framework allows food web models to include ontogenetic growth and
life-history omnivory at the individual level by resolving the population
structure of each species as a size-spectrum. Each species is characterised by
the trait 'size at maturation', and all model parameters are made species
independent through scaling with individual body size and size at maturation.
Parameter values are determined from cross-species analysis of fish communities
as life-history omnivory is widespread in aquatic systems, but may be
reparameterised for other systems. An ensemble of food webs is generated and
the resulting communities are analysed at four levels of organisation:
community level, species level, trait level, and individual level. The model
may be solved analytically by assuming that the community spectrum follows a
power law. The analytical solution provides a baseline expectation of the
results of complex food web simulations, and agrees well with the predictions
of the full model on 1) biomass distribution as a function of individual size,
2) biomass distribution as a function of size at maturation, and 3) relation
between predator-prey mass ratio of preferred and eaten food. The full model
additionally predicts the diversity distribution as a function of size at
maturation.
