A simple mathematical model upon the effect of predation by birds on a blue mussel (Mytilus edulis) population

A model on the dynamic relations between prey and predator is developed evaluating predation effects on a blue mussel (Mytilus edulis) population. It is based on the data gathered on a newly established mussel bed in the tidal flats of Lower Saxony, Germany. The hypothesis was tested that the predation pressure by birds had an important influence on the decrease of the mussel population. The quantitative effect of predation by herring gulls (Larus argentatus) and oystercatchers (Haematopus ostralegus) was very small. Modelling drew attention to the fact that mussels larger than the mean of the population were more often predated on by birds than mussels smaller than the mean. As a result, mussels of a population predated on by birds take longer to get large than of a population without predation.