Analysis of Red Sea fish species' introductions into the Mediterranean reveals shifts in introduction patterns

Abstract

Aim: The Mediterranean Sea is one of the most threatened marine systems in the world. One of the major threats is the introduction of alien species from the Red Sea through the Suez Canal into the Mediterranean. The aim of our study was to address two interrelated questions, namely which traits of Red Sea fish species are associated with the species' introduction into the Mediterranean Sea and how the introduction patterns changed over time. Location: Red Sea and Mediterranean Sea: Methods: We used Cox regressions to identify traits of Red Sea species that are associated with the rate at which new alien Red Sea species are recorded in the Mediterranean (hazard rate) and to identify groups of species with different temporal trends of their baseline hazard rates. We fitted latent-variable models to determine whether different trends in baseline hazard rates can be attributed to trends in detection or introduction. Results: Our results showed that the highest hazard rate occurred among pelagic species, species living over soft bottoms, species present in small families and species recorded in the Red Sea close to the Suez Canal. We also found that alien species could be separated into three groups with different temporal trends in baseline hazard rates. The different trends were due to changes in introduction rate rather than detection. Two groups with historically low introduction rate showed an increase in introduction rate over time. Main conclusions: Our results provide novel biogeographical explanations for introduction patterns that were previously attributed to the effects of sea surface temperature and interspecific competition. The trends uncovered by our analysis indicate that the profile of introduced species is changing with potentially profound consequences for the Mediterranean Sea. © 2016 John Wiley & Sons Ltd