Table 1.

The net production models of individual growth and reproduction. An animal assimilates carbon from food and uses it for basal maintenance. Net production, assimilation minus maintenance, represents surplus carbon that can be assigned to growth (i.e. production of new somatic tissue) or egg production. The ‘full’ model is that of Nisbet et al. (2004), the stage-structured model is a simplified version in which assimilation rates are assumed identical for the two life stages: juvenile and adult.

state variables	W = carbon content of animal (mgC)
	E = cumulative egg production (fecundity = dE/dt)
	X = density of food in the environment (mgC l−1)
rates	I = ingestion rate (mgC d−1)
	A = assimilation rate (mgC d−1)
	M = maintenance rate (mgC d−1)
	P = A − M = net production rate (mgC d−1)
balance equations		somatic growth (mgC d−1)
		egg production (number of eggs per day)
		food depletion (mgC d−1)
	X is reset to XR if t = nTR, where n is an integer	transfer culture conditions
model functions	W = ξLq	allometric (carbon) weight–length relation
	M = mW	maintenance rate proportional to weight (full net production model)
	M = 0	maintenance included in assimilation efficiency (stage-structured model)
	A = Am(W) f(X)	assimilation rate depends multiplicatively on size (carbon content) and food density
	with: Am(W) to be fitted	full net production model
	Θ(W) to be fitted	stage-structured model size-dependent allocation to growth
		Holling type 2 functional response
	parameters	ξ	parameter in carbon-length relation (mgC mm−q)
q		exponent in carbon-length relation (dimensionless)
Xh		half-saturation constant (mgC l−1)
we		carbon required for an egg (mgC)
m		specific maintenance rate (d−1)
AJ, AA		assimilation rates for juveniles and adults in the stage-structured model (mgC d−1)
ɛa		assimilation efficiency (dimensionless)
TR		interval between transfers to fresh food (day)
v		system volume (l)