Common traits associated with establishment and spread of Lessepsian fishes in the Mediterranean Sea

It was more than 30 years after the opening of the Suez Canal in 1869 that the first reports on Indo-Pacific fishes entering the Mediterranean Sea (so-called ‘Lessepsian migration’) were published. The number of new records of Lessepsian fishes remained more or less constant between 1920 and 2000 but increased dramatically after that. The accelerated rate of entry was attributed by many authors to an increase in the Mediterranean surface water temperature. However, the Suez Canal has been repeatedly deepened and widened during the last decades and the increased immigration rate of Red Sea fishes might also be related to reduced dispersal barriers. We analyse the relationship between dispersal and establishment success and a pool of different traits for 101 Lessepsian fish species using generalized linear models. Our models did not reveal a significant relationship between the sea surface temperature in the native range of immigrant fishes and their dispersal or establishment success in the Mediterranean Sea. The minimum depth in which a species was observed was the only significant trait influencing dispersal success. This trait is likely related to the architecture of the Suez Canal since until the 1970s only species with a very low minimum depth were recorded to have entered the Mediterranean, but species occurring in deeper water started to immigrate after 1980 when the canal was deepened to 19.5 m. The establishment success of Lessepsian fishes was significantly linked to size and spawning type. Benthic spawners and species with adhesive eggs represent successful colonizers. Moreover, successful colonizers are species with a tendency to form schools, whereas solitary species are less successful. The results show that dispersal and establishment success of Lessepsian fish immigrants are influenced by different ecological traits.