The Mediterranean Sea is a hotspot for biological invasions, particularly due to the influx of non-indigenous species from the Red Sea via the Suez Canal (Lessepsian migration). Cryptocentrus steinhardti, a shrimp-associated goby, was previously known only from three trawl-collected specimens off the Israeli coast, with no in situ observations and limited ecological information. Here, we report the first in situ records of C. steinhardti in the Mediterranean Sea, based on scuba observations conducted in the Bay of Kaş, Türkiye, between 2019 and 2025. These observations provide the first photographic and video documentation of the species in its natural Mediterranean habitat and constitute its first confirmed record in Turkish waters. Repeated sightings over multiple years suggest the presence of a locally established, low-density population. Individuals were observed at shallower depths (10-25 m) than previously reported and in association with the alpheid shrimp Alpheus cf. rapacida, confirming their symbiotic behaviour. Our findings indicate that C. steinhardti is established in the Mediterranean Sea and emphasize the value of in situ monitoring for assessing the ecology and spread of non-indigenous species.
Invasive alien species pose significant threats to marine biodiversity by altering ecosystem structure and function, outcompeting native species, transmitting diseases, or interbreeding with local fauna. The Mediterranean Sea is among the regions most affected by biological invasions and hosts one of the highest diversities of invasive crab species. One of the most widespread alien species is Percnon gibbesi, that has colonized and spread throughout the Mediterranean Sea over the last 25 years. This study provides the first genetic assessment of established P. gibbesi populations in the Mediterranean. Mitochondrial cytochrome oxidase subunit I (COI) gene sequences were obtained from individuals collected in Mediterranean populations and the Canary Islands and compared with those available in databases from the Azores and the Caribbean Sea. Phylogenetic relationships between native and invasive populations were assessed to determine the potential origin of the invasion and to trace the species’ expansion pathway across the Mediterranean. Our results show that populations from the Mediterranean, Canary Islands, and Azores clustered together, supporting an eastern Atlantic origin of the Mediterranean invasion. Phylogenetic and population genetic analyses revealed high haplotype diversity and a lack of significant population genetic structure. These patterns suggest sustained connectivity and rapid expansion within the invaded region. The observed genetic diversity is consistent with effective larval dispersal and potential anthropogenic transport contributing to the ongoing invasion.
A single specimen of the Blackbanded trevally, Seriolina nigrofasciata, was collected by spearfishing off Khaldeh, Lebanon, on 13 September 2025 at a depth of 16 m. The specimen was identified based on its distinctive morphology, meristic characters and colour pattern. Seriolina nigrofasciata is widely distributed in the Indo-West Pacific, including the Red Sea. This specimen represents the first documented record of S. nigrofasciata and of the monotypic genus Seriolina in the Mediterranean Sea. Passage through the Suez Canal is considered the most plausible introduction pathway because the species is native to the Red Sea and the specimen was collected in the Levantine Sea, where many Indo-Pacific fishes are first recorded. Shipping remains a possible alternative pathway. The capture of a single individual provides no evidence of establishment, and additional records, evidence of reproduction and genetic comparisons with populations from the Red Sea and other parts of the Indo-Pacific are required to clarify its geographic origin and status in the Mediterranean.
Larval fish assemblages are crucial indicators for monitoring marine ecosystem dynamics and the recruitment potential of fishery stocks. This study investigates the spatiotemporal dynamics of larval fish assemblages in the central Southern Black Sea (Sinop) and the environmental parameters shaping these patterns. An intra-annual monthly sampling survey identified 35 species across 20 families; the assemblage structure was dominated by Engraulis encrasicolus, Gobius niger, Sprattus sprattus, Mullus barbatus and Trachurus mediterraneus. Multivariate analyses revealed a clear temporal structuring of larval fish assemblages due to intra-annual variation. However, no significant spatial separation was observed among the stations. Distance-based Linear Models (DistLM) indicated that assemblage variability was primarily associated with salinity, chlorophyll a and temperature, as well as light transmission and current velocity. Species-specific responses of dominant taxa to environmental variables were examined using Generalized Additive Models (GAMs), revealing distinct environmental partitioning among species. Model results indicated that E. encrasicolus abundance was primarily associated with chlorophyll a and low salinity gradients, whereas G. niger exhibited a response to multiple variables, including low salinity, low light transmission, and a wide thermal range. Conversely, the distribution of S. sprattus was strictly limited by low temperatures and specific ranges of light transmission. These findings suggest that larval fish assemblages in the Southern Black Sea are structured by a complex combination of physical forcing (such as mesoscale hydrological features) and biological interactions, in which differentiated environmental responses facilitate species coexistence.
Libyan marine biodiversity is often described as under-studied and under-reported. However, in the past seven years, there has been a surge in the reporting of non-indigenous, and native species with the help of citizen science, social media mining-based research and field surveys. This review provides an updated checklist of non-indigenous fish species in Libyan waters. Between 2018 and July 2025, 14 non-indigenous species (NIS) and four range-expanding (RE) species were documented. Furthermore, between 2018 and July 2025, 27 species belonging to eight phyla (Porifera, Bryozoa, Tunicata, Cnidaria, Mollusca, Polychaeta, Decapoda, and Echinodermata) were recorded, including 23 NIS, one RE and three cryptogenic species. Additionally, this review paper draws a direct comparison between the scientific outcomes of citizen science, social media mining, and field surveys within the same time frame. The differences between the two main methods are discussed, with active and passive citizen science and social media mining produced the most non-indigenous fish species, while field surveys excelled in documenting native fish species, as well as small and minute species. Furthermore, this review addresses the implications of using citizen science and social media mining, pointing out the ethical concerns that have arisen from the methodologies observed in several scientific studies that employ these methods.
