An updated and evidence-based checklist of Mediterranean Sea fishes is provided. Each of the fish species in the Mediterranean Sea listed here was either listed in the last published checklist of the Mediterranean fishes or in other articles, reports or new records, and the checklist is critically assessed. Out of the assessed 791 species previously reported from the Mediterranean, the presence of 759 species is confirmed while 32 species are excluded from the new checklist, by lacking evidence of presence or representing obvious taxonomic confusions. The net increase in known Mediterranean fish species richness since the last checklist is 11%. The non-native Mediterranean species now represent 22.1% (168 species) of the known Mediterranean fish diversity. The evidence-based protocol applied here provides a reliable checklist of marine fishes, for which each of the included species has indeed been recorded at least once within the discussed geographic area in the Mediterranean Sea.

The current article presents 18 new records from seven Mediterranean countries. These records include one rhodophyte, fournudibranchs, two crustaceans, one stingray and 10 bony fishes. They are grouped by country as follows: Lebanon - first record ofthe Striped bass Morone saxatilis, the stingray Himantura leoparda, the Areolate grouper Epinephelus areolatus and the Spot-finporcupinefish Diodon hystrix from various parts of the country; Turkey - first record of the invasive red alga Grateloupia turuturufrom the sea of Marmara (region of Bandırma), the sea slug Goniobranchus obsoletus and the crab Arcania brevifrons from theGulf of Antalya and the cladoceran Pleopis schmackeri from several locations along the Aegean Sea; Cyprus - first record of thealien sea slug Berthellina citrina from the region of Cape Greco and an observation of a butterflyfish Heniochus sp. from the northeasternside of the island; Greece - first record of the alien sea slug Anteaeolidiella lurana from the region of Heraklion in Creteand the record of the Atlantic spadefish Chaetodipterus faber and the Black surgeonfish Acanthurus cfr gahhm from SalaminaIsland; Slovenia - first record of the alien sea slug Thecacera pennigera from Izola; Italy - first record of the hybrid Striped bass(Morone saxatilis × Morone chrysops) from the northern Tyrrhenian Sea and a first record of the goldfish Carassius auratus fromthe region of Apulia; Libya - first record of the Red Sea goatfish Parupeneus forsskali and the African surgeonfish Acanthurusmonroviae, respectively from the eastern (Al-Tamimi area) and the western shore (Al-Khums area).

Although there is a high number of publications listing fish species in the Adriatic, only a few have focused on chondrichthyans, while their conservation status has been investigated even less. Thus, this paper aims to provide an updated and annotated checklist of the chondrichthyans occurring in the Adriatic waters with their presence and conservation status. Each species is evaluated against the criteria defined in IUCN (International Union for Conservation of Nature) Red List Categories and Criteria and according to the guidelines for national and regional level assessments. In total, 60 chondrichthyan species from 27 families and 42 genera are listed. The list contains 33 species of sharks, 26 species of rays and one chimera. Assessment of the conservation status reveals that three species are now considered Regionally Extinct (namely Squatina oculata, Pristis pectinata and Rhinobatos rhinobatos). A total of 21 species are assessed as Critically Endangered, 8 are Endangered and 10 are Vulnerable. Of the remaining species, six are Near Threatened and the same number of species are Least Concern and Data Deficient. Considering that the principal driver of chondrichthyan decline and regional extinction is overfishing, it is recommended that the Adriatic countries adopt the same management measures and strengthen their coordination.

Globally, marine bioinvasions threaten marine ecosystem structure and function, with the Mediterranean Sea being one of the most affected regions. Such invasions are expected to increase due to climate change. We conducted a risk screening of marine organisms (37 fishes, 38 invertebrates, and 9 plants), both extant and ‘horizon’ (i.e., not present in the area but likely to enter it). Based on expert knowledge for the Eastern Adriatic Sea coasts of Slovenia, Croatia, and Montenegro, screenings were conducted under both current and predicted climate conditions indicating with an increase in sea surface temperature and salinity of the Adriatic Sea together with changes in precipitation regime. Our aims were to: (1) identify non-native extant and horizon marine species that may pose threats to native biodiversity and (2) evaluate the risk of invasiveness of the selected species under current and predicted climate conditions. Of the 84 species screened, there was an increase in those ranked as ‘high risk’ from 33 (39.3%) under current climate conditions and to 47 (56.0%) under global warming scenarios. For those ranked as ‘very high’ risk, the increase was from 6 (7.1%) to 21 (25.0%). Amongst the screened species, the already established high-risk species Pacific oyster Magallana gigas and Atlantic blue crab Callinectes sapidus represent a threat to ecosystem services. Given the under-representation of marine species in the current European Union List, the species we have ranked as high to very high risk should be included.

Marine phanerogams are considered biological sentinels or indicators since any modification in seagrass meadow distribution and coverage signals negative changes in the marine environment. In recent decades, seagrass meadows have undergone global losses at accelerating rates, and almost one-third of their coverage has disappeared globally. This study focused on the dynamics of seagrass meadows in the northern Adriatic Sea, which is one of the most anthropogenically affected areas in the Mediterranean Sea. Seagrass distribution data and remote sensing products were utilized to identify the stable and dynamic parts of the seagrass ecosystem. Different seagrass species could not be distinguished with the Sentinel-2 (BOA) satellite image. However, results revealed a generally stable seagrass meadow (283.5 Ha) but, on the other hand, a stochastic behavior in seagrass meadow retraction (90.8 Ha) linked to local environmental processes associated with anthropogenic activities or climate change. If systemized, this proposed approach to monitoring seagrass meadow dynamics could be developed as a spatial decision support system for the entire Mediterranean basin. Such a tool could serve as a key element for decision makers in marine protected areas and would potentially support more effective conservation and management actions in these highly productive and important environments.

The updated checklist of Adriatic Sea fishes with a critical assessment of each species using an evidence approach is provided. Each fish species in Adriatic Sea listed in the last published checklist and those reported in published new records not included in the most recent Adriatic checklist, have been included. Of the total of 466 fish species, the presence in the Adriatic Sea was confirmed for 444 species by at least one positive record of the species in the area, the presence of 10 species is still unconfirmed, and 12 fish species are excluded from the list. An evidence approach protocol is recommended for general use for compiling checklists of marine fishes.