Impact of Local Pollution on Fish Abundance Using Geostatistical Simulations

Abstract

The paper quantifies the impact of human activities on the abundance of fresh water fish populations. In the case of the Scorff river (Brittany, France), two punctual pollutions are caused by the discharges of two fish farms and generate two perturbed sections where salmon juvenile abundance is reduced. Assuming the pollution does not involve any change of salmon density in the unperturbed sections, geostatistical simulations have been used to quantify the impact of the fish farms on the abundance of salmon. To this end, spatial structures of densities are analysed and modelled for two different cases: one using all the data to describe the “actual structure”; one using only the unperturbed data to estimate the “possible structure” of juvenile salmon in the absence of pollution. In each case, the structural model is used to simulate what could be the distribution of juveniles in areas perturbed by the fish farms. The difference between simulations conditioned by all the data or only by the unperturbed data, allows us to quantify the impact of the fish farms in terms of numbers of juveniles lost.