Accounting for temporal and individual variation in the estimation of
Von Bertalanffy growth curves
Abstract
Growth and growth limitation are important indicators of density
dependence and environmental limitation of populations. Estimating
individual growth trajectories is therefore an important aspect of
understanding and predicting the life history and dynamics of a
population. Variation in individual growth trajectories arises due to
variation in the environmental factors limiting individual growth. This
environmental limitation can vary over time, between cohorts and between
individuals within a cohort. For a complete and accurate understanding
of individual growth in a population, it is important to include all
these sources of variation. So far, statistical models only accounted
for a subset of these factors or required an extensive growth history of
individuals. Here we present a novel model describing the growth curves
of cohorts in a population. This model is derived from a stochastic form
of the Von Bertalanffy growth equation describing individual growth. The
model is specifically tailored for use on length-at-age data in which
the growth trajectory of an individual is unknown and every individual
is only measured once. The presented method can also be used if growth
limitation differs strongly between age or length classes. We
demonstrate the use of the model for length-at-age data of North Sea
plaice (Pleuronectes platessa) from the last thirty years. Fitting this
model to length-at-age data can provide new insights in the dynamics of
the environmental factors limiting individual growth and provides a
useful tool for ecological research and management.