How to determine the likely indirect food-web consequences of a newly introduced non-native species: A worked example

The 'predicted' diet composition of F. commersonii derived from the RPA analysis was then used as input to an Ecopath with Ecosim (EwE) model. This model was used to simulate possible consequences of introducing this invasive species, assuming different rates of expansion of F. commersonii populations in the region. Increases in the F. commersonii population resulted in a marked decline in certain prey types (notably planktivorous fish, Mullus surmuletus and Symphodus tinca). By contrast, seabirds and piscivorous fish were suggested as possible beneficiaries, although this depended heavily on model and scenario assumptions. Overall fisheries catches were projected to increase, and this reflected an anticipated 'bottom up' increase in piscivorous fish that are the main target of the commercial fishery in the Bay of Calvi region.