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 We hereby report unpublished data for five NIS (the annelid Branchiomma luctuosum, the shrimp Saron marmoratus and the fishes Lutjanus argentimaculatus, Oxyurichthys petersii, and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.

Biological invasions constitute a major threat to native ecosystems and to global biodiversity

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”.

The monitoring of contaminants in fish species is pivotal for fishes’ health and reproduction, as well as for human health. In the specific work, three major categories of contaminants, pesticides, pharmaceuticals, and macro and trace elements, were investigated in two major fish species, Dicentrarchus labrax and Solea solea, collected from Thermaikos Gulf, in Greece. To achieve this goal, three analytical methods using LC-MS/MS, GC-MS/MS, and ICP-MS were developed, validated, and applied to the collected fish samples. The results indicated a very low prevalence of caffeine and acetaminophen, both not exceeding 3.8 μg/kg fish. Similarly, thiabendazole, cypermethrin, and tricyclazole (pesticides) were found in a concentration range of 0.9 to 13.7 μg/kg fish, while in one D. labrax sample, traces of the metabolite of organochlorine pesticide DDT, o,p’-DDE were detected. Al, Mn, Fe, Zn, and Sr were the predominant trace elements in a concentration range of 500–20,000 μg/kg fish. Macro elements levels varied from 280 to 5405 mg/kg fish. Health risk assessment did not unveil an unacceptable risk for the human health of adults, apart from one sample presenting Hg above the regulatory levels. On the contrary, for children, the calculated hazard quotient values for Hg in all cases and for two As detections were higher than the threshold value of 1, indicating a potential risk.

Marine invasive alien species (IAS) are spreading in the Mediterranean Sea, altering species composition and reshaping marine ecosystems. The study explores consumer attitudes towards the consumption of marine invasive alien species (IAS), particularly lionfish and Atlantic blue crab, in the Greek seafood market. These species are considered a threat to marine biodiversity but are also being considered for commercial seafood to mitigate their ecological impact. Through surveys of consumers and seafood retailers, the research finds that while Greek consumers show a positive attitude towards consuming these species, they often lack awareness of their ecological impact. Retailers see potential in promoting these invasive species, with freshness, hygiene, and poison concerns being the most important factors for consumers when purchasing seafood. In general, there is a need for better public education regarding the ecological and health impacts of IAS consumption. Factors that could increase consumption include recommendations from seafood retailers, promotion by TV cooking shows, and quality certifications. The study suggests that aligning consumer education with conservation goals could help control the spread of IAS while supporting local fisheries.