Dual Migrations Threaten Local Diversity in the Mediterranean: A Case Study from Syrian Marine Waters

Syrian marine waters represent an essential part of the Levantine Basin. From 2022 to 2025, numerous reports have indicated an increasing influx of non-indigenous species into the Mediterranean Sea. Non-indigenous fish species were recorded and captured using different types of fishing gear (such as spearfishing, fish traps, and trawling nets) at various depths. FAO taxonomic keys were utilized following morphometric measurements and diagnostic character examinations to identify species accurately. The taxonomic identifications were verified and documented against the peer-reviewed literature. The specimens were preserved in 10% formalin and are deposited in the Marine Science Laboratory, Faculty of Agricultural Engineering, Latakia University, Latakia, Syria. As a result, a total of six non-indigenous fish species were recorded and documented from Syrian marine waters. Four of them (Heniochus intermedius, Lutjanus fulviflamma, Epinephelus areolatus, and Synanceia verrucosa) are from the Indo-Pacific Ocean, while only two species (Symphodus bailloni and Naucrates ductor) are from the Atlantic Ocean. This migration has resulted from a combination of human activities—such as marine transport, the aquarium trade, and the Suez Canal—alongside climate change. Climate change plays an essential role by removing natural thermal barriers; elevated temperatures weaken indigenous fishes, obliging them to vacate their ecological niches to these alien species instead of resisting them. Together, this combination contributes to creating suitable environmental conditions for these alien fishes. In conclusion, this continuous dual migration will change the overall composition of fishes in the Mediterranean, potentially turning the area into a unique, modified ecosystem in the coming years. This escalating issue requires continuous international and regional efforts in fisheries management and biodiversity conservation.