Updated assessment of the distribution, status and impacts of marine non-indigenous and other newcomer species in the Maltese waters

Abstract

The latest inventory on all newcomer species in Maltese waters dates back from 2015. Several new or additional records of alien and range-expanding species have been reported since, necessitating an update to this work, while no comprehensive assessment of the distribution patterns and impacts of non-indigenous species (NIS) in Maltese waters has been published to date. This project will update and re-evaluate the inventory and compare it to the previous one. The coordinates from the records will be used to look at spatial patterns, and to identify hotspots. Through literature studies the environmental impacts will be assessed. The inventory has increased to 106 species, of which most are still considered casual newcomer species, but the amount of invasive species has increased by two. The amount of unknown pathways has decreased and shipping is the most prominent mode of entry into the Maltese waters. The spatial pattern of the records, show that the harbours are hotspots of NIS, which is also explained by the shipping pathway. Another spatial pattern was the records being in the vicinity of popular diving spots. There is a huge bias in the known literature, since absence of an NIS is not recorded often, and the locations cover the same areas and don’t cover hard to reach coastlines, like the Dingli cliffs. The records of invasive species are not a perfect tool to track the dispersal, since they are often discovered after reaching the establishment phase. The inventory needs to be kept updated, to track the status of the Maltese waters and more information should be collected on ecological impact of the newcomer species.