Depletion fishing of the alien fish species Siganus luridus, S. rivulatus, Pterois miles, and Etrumeus golanii in the Mediterranean Sea-gear, ecosystem impacts, and resolution

Abstract

S. luridus, S. rivulatus, P. miles, and E. golanii are four Lessepsians among the approximately 90 alien fish and have already demonstrated detectable negative impacts on local fish stocks and ecosystems in the Mediterranean Sea. The purpose of this review is to evaluate the feasibility and sustainability of their eradication through depletion fishing based on available knowledge and practices because there is positive mutual reinforcement between the altered state of a marine ecosystem due to changes in biogeochemical cycling and fishing and aliens’ establishment. Mediterranean artisanal and recreational fisheries already use efficient fishing gear, namely gill and trammel nets for S. luridus and S. rivulatus, spearguns for P. miles, and pelagic trawls for E. golanii. Removal of the aliens of concern restores local fish populations in field and modeling studies but the effects appear not to be long-lasting due to hydrodynamic connectivity with source populations and insufficient local natural mortality and predation either at the early (egg, larva) or later (juvenile, adult) stages of the aliens’ growth. Τo transcend the goal of management from local control toward resolution for these four Lessepsians’ entry and establishment in the Mediterranean Sea, the re-active intervention of their depletion fishing needs to be aligned with pro-active interventions at their sources of entry and means of transport upstream and with inter-active interventions of their monitoring by the multiple active users of marine resources. Sustainability of the resolution goal will be ensured provided it is designed in the large Mediterranean marine ecosystem jurisdiction, which includes both sources and sinks of aliens; planned locally, which caters for differential effects of aliens on local ecologies, societies, and economies; and considers mediators and moderators of the whole context of multiple-source, multiple-sector, nascent alien trophic web, and altered state of local ecosystems.