This work presents refined, updated subregional and regional non-indigenous species (NIS) inventories for the Mediterranean Sea, validated by national and taxonomic experts, with species records observed until December 2020. These datasets will be used as the baselines for the implementation of the Integrated Monitoring and Assessment Programme for the Mediterranean (IMAP) and the Mediterranean Quality Status Report 2023. In total, 1006 non-indigenous species have been found in Mediterranean marine and brackish waters. The highest numbers of NIS were observed in Israel, Türkiye, Lebanon and Italy. Approximately 45 species were categorized as data deficient, either due to lack of consensus on their alien status or the validity of their identification. Polychaeta, Foraminifera and macroalgae were the groups with the highest numbers of controversial species. There was a general increase in the yearly rate of new NIS introductions after the late 1990s, which appears to be slowing down in the last decade, but this may be confounded by reporting lags and differential research efforts. Between 1970 and 2020 there has been a steep increase in the proportion of shared species present throughout all four Mediterranean subregions, which are predominantly transported via shipping and recreational boating. While Lessepsian species are gradually spreading westwards and northwards, there is still a considerable invasion debt accumulating in the eastern and central Mediterranean.

Torquigener flavimaculosus Hardy & Randall (1983) was described based on specimens collected from the Gulf of Aqaba, Gulf of Suez, and Gulf of Aden, which has then penetrated the Mediterranean Sea, becoming one of the most abundant invasive tetraodontids. A comparison of samples collected from the northern Levant coasts of Türkiye between 2007 and 2020 showed that morphometric and meristic characteristics do not fully match either with T. flavimaculosus, or the closely related congeneric species T. hypselogeneion and T. altipinnis. Multivariate analysis carried out by 16 morphometric and six meristic characters did not show any discrimination between the above-mentioned species and exhibited almost identical sequences in genetic analysis. The results strongly suggest that T. flavimaculosus and T. hypselogeneion are conspecific, making the former species a junior synonym of the latter.

The silver-cheeked toadfish Lagocephalus sceleratus (Gmelin 1789), and to a lesser degree the orange spotted toadfish Torquigener hypselogeneion (Bleeker, 1852), pose threats to human health from physical attacks and poisonings in the Eastern Mediterranean Sea. This study reviewed human health-related impacts resulting from these pufferfish, compiling and assessing records from online sources, the peer-reviewed literature, medical records, personal interviews, and observations across the Eastern Mediterranean in the years 2004 to 2023. A total of 198 events impacting human health were documented: 28 records of physical attacks, at least 144 non-lethal poisoning episodes, and 27 human fatalities resulting from consumption. The majority of the reported incidences occurred in Syria, Türkiye, and Lebanon. Most physical attacks occurred in summer, while most poisoning events occurred during winter. The number of recorded incidents greatly increased after 2019, especially with regard to poisonings, yet whether this is related to greater media attention, or to increased fish abundance is unclear. This is the first comprehensive study to collate findings on attacks, poisonings and fatalities caused by these pufferfish in the Mediterranean Sea, and may help in improving national health policies. We urge the continuation of national campaigns to caution residents and tourists of these species’ high toxicities and potential aggressiveness.

This study presents the first comprehensive assessment of alien species occurrences within the selected 11 Marine Protected Areas (MPAs) located on the Aegean and Levantine coasts of Turkey. The inventory includes a total of 289 species belonging to 15 phyla, in which lowest and highest diversities were observed in Saros Bay MPA (27 species, northern Aegean Sea) and Fethiye-Göcek Bay MPA (150 species, northwest Levantine Sea), respectively. Alien species distributions that were revealed in protected areas located in the southern Aegean and Levantine Seas were 56.9% similar (based on presence vs. absence data), while northern Aegean sites formed another distinct group. According to the breakdown of major phyla through the entire study areas, Mollusca had the highest alien diversity (22.1% of alien species), followed by Actinopterygii (19.0%), Arthropoda (15.2%) and Annelida (13.5%). Casual aliens were represented by very low proportions in each MPA, proving that most species were already established in the region, with a significant proportion of invasive species. Regardless of the localities, the majority of the species originated from the Red Sea, whose primary pathway of introduction is the corridor, the Suez Canal. In the absence of effective management actions against bioinvasions, MPAs located along the Turkish coastline do not currently seem to provide any protection, revealing a large conservation gap to be filled.

After the description of Gobius incognitus Kovačić & Šanda, 2016, all previous knowledge about the geographic distribution of Gobius bucchichi Steindachner, 1870, as well as its ecology and biology, became obsolete, since it represented the data from the mixture of two species. The known geographic distribution of G. bucchichi and G. incognitus is revisited by validating previously published records, but also and foremost by integrating many new photographic records posted by anglers and divers on social media and on citizen science databases. The present research uses only positively identified records with exact data on locality, coordinates and date of collecting. A total of 1024 confirmed records were collected and retained for inferring distribution maps: 805 records of G. incognitus and 219 records of G. bucchichi. Gobius incognitus is a widespread Mediterranean Sea species with limited presence in the Lusitanian province of the Eastern Atlantic Ocean. It is absent from the Sea of Marmara and the Black Sea. Gobius bucchichi is recorded only in the eastern half of the Mediterranean Sea, from the Adriatic to the Aegean Sea, and in the Black Sea and Sea of Marmara.

Diplecogaster umutturali sp. n. is described from five specimens, ranging from 9.5 to 26.9 mm in standard length. This clingfish is known to occur only at three localities along the northern Levant coasts, eastern Mediterranean Sea and is the third known species of the genus Diplecogaster in the Mediterranean and Black Seas. The species is distinguished from all its congeners in having a small snout, short caudal peduncle, large eyes, short anal fin and upper attachment of gill membrane opposite the 7th-8th pectoral ray. Diplecogaster umutturali sp. n. shows a 5.3% genetic divergence from its close relative D. bimaculata at the cytochrome oxidase I locus (COI). http://www.zoobank.org/urn:lsid:zoobank.org:pub:376298FE-C8A7-44BB-9B12-721E41D7F355