The migration of Lessepsian species, which was the result of the opening of the Suez Canal in 1869 and further facilitated by human activities and environmental conditions, seems to play a key role for fisheries particularly in the Levant basin. However, there is still lack of accurate data for most of the Lessepsian species in order to evaluate their positive or negative effect to the fisheries catches and local fish stocks. The Project "Scientific and Institutional Cooperation to Support Responsible Fisheries in the Eastern Mediterranean- EastMed has been declared in September 2009, is executed by the Food and Agriculture Organization of the United Nations (FAO) and funded by Greece, Italy and EC. A network of experts on the effect of Lessepsian species on fisheries of the Eastern Mediterranean (NELESFISH) was established following a sub-regional technical meeting of the FAO-EastMed Project on "The Lessepsian Migration and its Impact on Eastern Mediterranean Fishery", that took place in Nicosia, Cyprus, in December 2010 and was attended by experts from Cyprus, Egypt, Gaza Strip and West bank, Greece, Italy, Lebanon and Turkey. According to the review of available information during the meeting, the Lessepsian migrants caught by fishing gears include nowadays 77 fish and 24 invertebrate species; their numbers are increasing from year to year. Some Lessepsian species, like Siganus spp., Marsupenaeus japonicus, Saurida undosquamis, Etrumeus terres, Upeneus spp., have been successfully introduced into local markets, constituting important resources for fisheries in some countries. Others, like Fistularia commersoni, are landed or discarded depending on the demand in the local markets and require some marketing to increase their commercialization. Some venomous species, like for example Lagocephalus sceleratus and Rhopilema nomadica, apart from being hazardous to human health, are causing damages to fishing gears and commercial catches, particularly of some coastal fisheries in the Levant basin. Among the main objectives of the network of experts are the standardization of methodology for the collection of data aiming to the quantification of Lessepsian migrants and their effects on fisheries, the development of a database with relative literature and legislation and the contribution of recommendations within the framework of the FAO EastMed project towards the minimization of negative effects of Lessepsian migration and the adaptation of fisheries to this phenomenon.