Distribution of Lessepsian migrant fish in the Mediterranean

The las decade has seen a considerable increase in the amount of ichthyofaunistic studies throughout the countries of the Eastern Mediterranean. As a result, we now have a more accurate picture of the distribution of Red Sea fishes (Lessepsian migrants) in the region. A clear gradient emerges, with 54 substantiated records on th; Israeli-Lebanese coast. The gradient decreases along the northern and southern coast of the eastern Mediterranean, as distribution spreads westward. Only four Lessepsian fish species have bern found in the central region and, to date, none in the western basin. These 54 species represent 36 families, of which 13 are new to the Mediterranean. The primary factors limiting distribution are thr presence of an adequate continental shelf, which is the habitat most prone to Lessepsian colonization, and the temperature regime. Cooler temperatures constitute a physiological constraint to fish of tropical origin. A biological sun ey of the Lessepsian fishes along the coast of Israel indicates that those species whose spawning seasons commence in early (i.e. cooler) months are more likely to br successful in spreading westward.