Modelling the role of alien species and fisheries in an Eastern Mediterranean insular shelf ecosystem

Abstract

We developed a trophic mass-balance model to describe the structure and functioning of the insular shelf ecosystem of the Republic of Cyprus and assess the impact of fishing and alien species during the mid-2010s. A total of 40 functional groups were defined, ranging from producers and detritus to top predators and when possible, alien species were included in exclusively alien groups. All fishing activities in the area were considered. Input data were obtained from local surveys, fishery statistics, published data on stomach content analyses, other scientific and grey literature, as well as empirical equations. Results show that the ecosystem shares common structural and functional characteristics with other Mediterranean ones, especially those in the eastern basin. Fishing has noticeable impacts on the ecosystem and based on the results, 7.1% of the total primary production is required to sustain fisheries. The model predicts a strong negative impact of small-scale fisheries on small sharks and turtles, and of recreational fisheries on the large demersal and pelagic fishes. Our results also highlight the significant role of alien species within the ecosystem. Alien fish accounted for 29% of fish production. Negative impacts of alien fish were predicted, in particular by alien siganids on phytobenthos, and some alien demersal fishes on eels and morays. This is the first food-web model for Cyprus and results are discussed and compared to other Mediterranean models.