Stochastic modelling for determining zooplankton abundance

The most reliable method for studying the dynamic behaviour of a population of organisms in a marine pelagic environment is to analyse the biomass or the abundance spectra. The spectra presented in semi logarithmic scale features the measurement variability as a reversed cone embodying the recorded abundances. This distribution in data variability motivated us to propose the existence of a process uncertainty.To analyse abundance spectra in stochastic context, we propose a compartmental configuration in which, at a given time, marine organisms are located according to their size in the compartments of a compartmental chain. The movement of organisms across compartments is described in probabilistic terms expressing transfer probabilities. The model considered at steady state allows the expression of the process uncertainty and the construction of the confidence corridors embodying the abundance spectra data.The developed model may be used for comparison of several collections of data, for analysis of environmental factors influencing the marine populations, or for new developments involving longitudinal data.