Individual-based model of the phenology of egg-bearing copepods: Application to Eurytemora affinis from the Seine estuary, France

Abstract

This study presents a non-spatial and temperature-dependent population model to better understand the population dynamics of the copepod Eurytemora affinis in the Seine estuary. The proposed individual-based model (IBM) allows each life-stage, or group of stages, to be represented and considers the differences in development rates and mortality caused by temperature and predation. The biological functions of the model were selected and calibrated to ensure realistic development at the temperatures recorded in the Seine estuary. The effect of temperature on development time and clutch size (CS) were obtained indirectly by fitting equations to the durations of stages observed in the laboratory at various temperatures and to CSs observed in the field. The degree-day approach was used to consider temperature variations. Mortality from predation was parameterized using the observed abundance of key predators. The proposed model successfully reproduces the life-history timing of the E. affinis population observed in the Seine estuary. The IBM approach was also used to simulate the development of the E. affinis population over several years at various temperatures with unlimited food conditions and no density dependence. The results confirm that the proposed model captures the role of temperature and predation in driving the seasonal population dynamics of E. affinis in the Seine estuary. This tool could be applied to any other egg-bearing copepods or could be used to test various E. affinis development scenarios in estuaries. This study also provides examples showing increasing temperatures and predation pressure shifts.