Accurate checklists of species are essential for evaluating their conservation status and for understanding more about their distribution, biology and ecology and, therefore, the first step in order to effectively protect them. According to the existing literature, the Greek seas are rich in chondrichthyan biodiversity and herein, we update the most recent chondrichthyan checklist for the country regarding the species that are present in the Greek waters, correct unvalidated miscellaneous sightings and observations and provide guidelines about future research to improve their conservation. In total, 330 sources were collected from which 276 were used for further analysis, resulting in 1485 records of 67 species, among which 61 are confirmed by experts, including 34 sharks, 26 batoids and one chimaera. We are further listing six species as “Questionable/Not Confirmed”.

In the Mediterranean Sea, Lobotes surinamensis (Bloch, 1790) is considered as a rare species, albeit an increasing number of individual-based sightings published in the literature. In this study, we present 32 additional records of this thermophilic species from the Greek and Cypriot waters; reinforcing the evidence that the species is becoming more common to the region. All of the records were collected as part of the citizen science project "Is it Alien to you? Share it!!!" by a participatory process involving fishers and taxonomic experts. This work highlights the important role of citizen science as a tool for public engagement and for monitoring species distribution in a changing environment, like the Mediterranean basin.

Raising knowledge of the dispersal of non-indigenous species (NIS) in new geographic areas is a matter of major concern, as alien species may outcompete the native biota through competition, predation, and hybridization. In the Mediterranean Sea, where biological invasions constitute a serious threat, the combined use of citizen science and social networks amplified the results obtained via traditional research activities, often recording species that would otherwise presumably have passed unnoticed. We hereby report unpublished data for five NIS (the annelid Branchiomma luctuosum, the shrimp Saron marmoratus and the fishes Lutjanus argentimaculatus, Oxyurichthys petersii, and specimens of the group of Abudefduf saxatilis/vaigiensis/troschelii) and one neo-native species (Seriola fasciata) in Greece and Cyprus (eastern Mediterranean Sea), the majority of which were obtained via a focused citizen-science project and constitute new records at a country level. We also revise and update their known distribution in the invaded area, thus contributing to the study of large-scale and well-defined distributional patterns of alien species spreading in the Mediterranean Sea.

Angel sharks are among the most threatened species of sharks globally. Twenty-two species have been identified globally so far, with three species being present in the Mediterranean Sea: Squatina aculeata, Squatina oculata, and Squatina squatina. The Mediterranean populations of all three species have been assessed as Critically Endangered by the IUCN Red List of Threatened Species due to the steep decline of their populations as a result of their historical and current overexploitation by demersal fisheries. Therefore, currently there is an ongoing increasing effort for advancing the conservation of the species in the basin. Recently, in the context of the Regional Action Plan for Mediterranean Angel Sharks, the Aegean Sea and Crete have been identified as critical areas for all three species. This study provides the first predictive distribution map of the three angel shark species in the basin, while critical areas for the conservation of the species were identified through a systematic spatial conservation planning analysis. Our analysis revealed low overlapping between the existing MPA network and critical areas for the distribution of the species primarily in Greece and then Turkey, while 20% of the critical areas for the distribution of the species overlaps with Fisheries Restricted Areas of the region. This highlights the need for creating MPAs focusing on shark conservation within the Mediterranean that are currently completely absent. In addition, we provide policy recommendations that can secure better protection of angel sharks through the enforcement of the current legislations and the engagement of all relevant stakeholders.

Biological invasions are considered among the largest threats to native biodiversity. The Mediterranean Sea, connecting the Indo-Pacific and Atlantic oceans, is characterized as a global marine invasion hotspot, due to a multitude of human pathways and vectors such as shipping, aquaculture, tourism, and the opening of the Suez Canal, which have led to the introduction of nearly 700 alien species into the Mediterranean Sea. Among the species introduced, the lionfish Pterois miles could be considered the fastest spreading invasive fish species of the last decade (2012–2022) and has been recorded in all countries of the eastern Mediterranean Sea, reaching as far north as Croatia. Here, we present a Bayesian additive regression tree modelling framework for an updated species distribution modelling invasion map under current and future climate conditions. All climate uncertainty sources have been used, as these are available from the Bio-Oracle, the unique marine predictors database. Important outputs of the current approach are the model’s inadequacy to accurately predict the most recent expansion of species in the Adriatic Sea, and the uncertainty estimation, that are high in areas with confirmed occurrence of individuals, in simulations that can help the decision makers and policy officers understand model limitations and take more informed actions.