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.
Taxonomy has long been guided by natural scientists whose choices, methods, and values shape how biodiversity is named and used today. This study reconstructs the making of one regional fauna, the endemic freshwater fishes now recognized from the territory of the modern Greek state, focusing on the researchers who collected and described these species and how they shaped freshwater fish systematics. We review sources screened through 2025 and analyze the description record of endemic species, which extends from 1837 to 2017. Using a dataset of 91 valid endemic species and 47 scientists, we examine who named what, when, and under which institutional, linguistic, and political conditions. For each species, we traced nomenclatural history, type locality, publication type and language; for each author, we compiled demographics, nationality, affiliations, discipline, and fieldwork activity, cross-checking multiple sources and, where possible, verifying details directly with living authors. Species descriptions accumulated in uneven pulses. The slow early phase was dominated by non-domestic expeditions (1830s-1900s). A pronounced interwar peak (1920s-1930s) was led by Balkan and Greek scientists, followed by wartime contraction (1940s). Renewed momentum followed the post-war decades and especially after 2000 as analytical tools improved. Authorship was highly skewed, with four prolific contributors (Karaman, Stephanidis, Economidis and Kottelat) producing nearly two-thirds of the names. Publication practices shifted gradually from monographs to serials, and from German to English, while about three-quarters of original combinations changed at least once. Overall, this study offers a people-centred baseline for Greek freshwater ichthyology, honoring its pioneers and showing how methods, taxonomic concepts, and cultural influences co-evolved. Within this context, it aims also to inform broader discussions on how taxonomic knowledge is formed and sustained within specific historical settings.
The thornback ray, Raja clavata Linnaeus, 1758, is the most commonly landed batoid species in bottom trawl fisheries of the Balearic Islands. Its commercial importance has led to unsustainable exploitation in recent decades, potentially threatening population stability. This study aims to estimate key biological and ecological parameters of this species in the Balearic Islands, including bathymetric distribution, reproduction, growth, and diet. Biological sampling was carried out with 776 individuals (11-95 cm length) obtained from MEDITS scientific surveys (2021-2024) and commercial catches (2022-2024). Young-of-the-year, juvenile, and adult populations were not bathymetrically segregated. Four growth models (two-parameter and three-parameter von Bertalanffy, Logistic, and Gompertz models) were fitted to age data derived from readings of vertebrae growth bands. The estimated L-50 values were 77.4 cm for females and 63.4 cm for males, while the corresponding A(50) values were 11 years and 8 years, respectively. The presence of active males and females, as well as the year-round occurrence of egg capsules, suggests a continuous reproductive cycle for the species. Stomach content analysis of 928 individuals revealed a marked ontogenetic dietary shift from small crustaceans to fish, occurring earlier in males (similar to 50 cm TL) than in females (similar to 60 cm TL); this shift preceded sexual maturation with no associated bathymetric segregation. A better understanding of the species' biology and ecology in the Balearic Islands will help improve stock assessments and support effective management and conservation measures.
The Mediterranean coral Cladocora caespitosa is a key species in temperate marine ecosystems, contributing to reef-building processes. However, it faces increasing threats from climate change, pollution, and human activities, in shallow coastal areas in particular This study presents a baseline monitoring project implemented in the Amvrakikos Gulf, Greece, in order to assess the distribution, health, and environmental drivers of C. caespitosa. A total of 26 sampling sites were surveyed across different depth zones and substrate types. Data collection included photographic documentation, in-situ morphometric measurements, and qualitative assessment of colonies at different substrate types and depths. The results show that the colonies on rocky substrates were significantly larger (118.2 +/- 53.0 mm) than those on mixed rocky-sandy substrates (67.7 +/- 44.8 mm). The average colony density across sites was 0.217 colonies/m2, while only 12.5% of colonies were classified as fully healthy, with 56.05% exhibiting partial mortality. As expected, substrate type and depth were identified as key drivers of coral health and morphology. These findings provide useful baseline insights for conservation and management strategies, particularly for semi-enclosed Mediterranean basins vulnerable to climate change.
ARCHELON’s Sea Turtle Rescue Centre (STRC) was established in 1994 in Glyfada, Attica, with the main objectives to rehabilitate injured turtles, assist in determining their threats at sea, and contribute to public awareness. Here, we present the main results of the STRC’s 30-year (1995-2024) operation, evaluating its rehabilitation effectiveness and drawing conclusions on the main threats that turtles encounter in the Greek seas. During this period, 1,539 turtle admissions were registered, with annual numbers showing a significant positive trend. Clinical examination identified the cause of injury for 87% of admissions, with 87.3% of them assigned to fisheries interaction (n=1,170), including those bearing injuries inflicted intentionally following incidental capture (n=595). In total, more than 71% of turtles rehabilitated for more than five days were released to the wild (n=842). Released turtles generally exhibited positive post-release behaviour as indicated by subsequent observations (live sightings or nesting activity) and by satellite telemetry, although more research is needed to confirm this, especially in the case of head traumas. Notwithstanding the relatively small number of released turtles, contributing modestly to sea turtle conservation in terms of increasing population viability and abundance, the role of the STRC is paramount in covering the social need for wildlife welfare, as well as being an important vehicle of public awareness and education.
The blue crab Callinectes sapidus, originally native to the western Atlantic coast, is a well-established invasive species along the Atlantic and Mediterranean coasts of Morocco. This study aimed to investigate the reproductive traits of C. sapidus along the Moroccan Mediterranean coast, specifically in the Marchica Lagoon, to support post-border biosecurity strategies. The research focused on estimating the gonadosomatic index (GSI), identifying the spawning season, and determining the size at first maturity of female C. sapidus. Monthly samples were collected as bycatch of artisanal fishers operating in the lagoon between May 2022 and April 2024. A total of 938 crabs were collected, with an average carapace width (CW) of 119.46 +/- 36.65 mm, carapace length (CL) of 54.11 +/- 15.68 mm, and body weight of 164.20 +/- 129.16 g. The sex ratio was significantly skewed toward males (1.36:1). Ovigerous females were observed from April to October, with two spawning peaks: the first in April and a more pronounced one in July to August, indicated by increased gonadosomatic index and a higher proportion of ovigerous females. The carapace width at 50% maturity (L50) was 114.4 mm overall, with females maturing at a larger size (117.8 mm) than males (111.1 mm). These findings provide a foundation for developing targeted strategies to manage the spread of C. sapidus in the Marchica Lagoon, reduce its population, and mitigate environmental impacts. They also highlight the potential to valorize the species as a fishery resource, potentially turning its management into an economic and ecological advantage.
The whale shark (Rhincodon typus) is the largest living fish species and a cosmopolitan planktivore primarily inhabiting tropical and warm-temperate waters. In most checklists it is generally considered absent from the Mediterranean Sea, although isolated sightings have been reported in recent years. Here we present the first confirmed records of R. typus from the southeastern Levantine coast, with multiple observations of two distinct individuals between September and November 2025. These sightings are added to the few existing records from Turkey (Samanda & gbreve;, Hatay, 2021) and Spain (Ceuta, Strait of Gibraltar, 2022). They also raise questions regarding the species' distribution across the Mediterranean and the origin of these individuals, which may have entered through the Suez Canal (Lessepsian migration) or from the Atlantic Ocean via the Strait of Gibraltar. These records may reflect ongoing changes in the Mediterranean Sea and highlight the importance of continued monitoring.
A series of sampling activities in the Tyre Coast Nature Reserve, on the Southern coast of Lebanon, in the context of the project Blue Tyre - Local Partnership for Sustainable Marine and Coastal Development, allowed for the collection of material to study the polychaete fauna of the area, with particular focus on Non-Indigenous Species (NIS). The detection of several taxonomical novelties resulted in the description of five new species belonging to four families: Dorvilleidae, Eunicidae, Nereididae, and Sabellidae. Based on clear differences compared to the historical polychaete fauna of the Mediterranean Sea and on the presence of morphological similarities or genetic correspondence with Indo-Pacific taxa, we suggest that, despite having Mediterranean type locality, the newly described species should be considered NIS in the Mediterranean. Thus, the present data reaffirm the importance of the Levantine Sea and the Lebanese coast as an outpost for the early tracking of bioinvasions in the Mediterranean area. Specific epithets of Pseudobranchiomma Jones, 1962 species are amended to their correct Latin gender, following article 30.1.2 of the I.Z.C.N. Lastly, a review of the available literature on both the genera Nereis Linnaeus, 1758 and Lysidice Lamarck, 1818 reveals the necessity of corrections to the taxonomic status of some species within these genera.
This study offers the first detailed investigation of the ichthyofauna of the K & uuml;& ccedil;& uuml;k & ccedil;ekmece Lagoon (& Idot;stanbul, T & uuml;rkiye) in nearly 30 years, with the aim of characterizing the current structure of the fish community in this anthropogenically pressured lagoon. Seasonal samplings were conducted between September 2023 and August 2024, and fishing was conducted at five different stations within the lagoon using multimesh gillnets and at two coastal sites using a seine net. A total of 18 fish species belonging to 12 families were identified. Only five species (Atherina pontica, Engraulis encrasicolus, Chelon auratus, Chelon ramada, and Mugil cephalus) were captured using gillnets. On the other hand, 17 species were recorded with a seine net in areas close to the lagoon's connection with the Sea of Marmara. Atherina pontica was the most abundant species in both fishing methods, while Salaria pavo, Belone belone Neogobius fluviatilis, Gobius niger, and Sparus aurata were each represented by a single specimen. The current species composition indicates a community dominated by euryhaline species, which differs from historical records that included freshwater taxa. The absence of freshwater species in the catch coincides with the observed salinity levels (up to 14.12). Except for a few resident species (e.g., A. pontica and E. encrasicolus), the lagoon is predominantly inhabited by euryhaline species, especially during spring and summer. Serving as a structured baseline, this study documents the current ecological status of fish assemblages in the lagoon following long-term environmental change.
The European flat oyster ( (Ostrea edulis Linnaeus, 1758) is a native bivalve of high ecological and economic importance in European marine ecosystems. Overexploitation, combined with widespread disease outbreaks in the 1970s, has caused a severe decline throughout its historical range, leaving many populations critically depleted or functionally extinct. This study assesses the status of remnant natural O. edulis populations inhabiting deeper subtidal habitats (similar to 30 m depth) in the northern Adriatic Sea, a region where O. edulis was abundant until relatively recently but has shown a pronounced decline over the last decade. We combined an extensive literature review with field surveys using beam trawl sampling and observations from a remotely operated vehicle (ROV). Analyses focused on oyster distribution, biomass indices, natural settlement substrates, and associated macrobenthic communities. Our results indicate a substantial decline in O. edulis biomass over the past decade, although small remnant populations persist within the study area. ROV surveys conducted at sites where fishing pressure has been eliminated, including historically abundant grounds, reveal no clear signs of population recovery. These findings suggest that reduced fishing pressure alone is insufficient to restore O. edulis populations. The results highlight the need for coordinated, region-wide monitoring and emphasise the importance of habitat availability, recruitment dynamics, and interactions with local aquaculture practices when developing effective conservation and restoration strategies for O. edulis in the Adriatic Sea.
Biomarkers are increasingly recognized as sensitive indicators of physiological and ecological responses in marine organisms, offering new perspectives for monitoring and ecosystem status assessment. Traditional indices of species composition and biomass, though valuable, often fail to capture early sublethal or functional changes in zooplankton communities. To explore the potential of biomarkers as complementary tools for environmental monitoring within the European Marine Strategy Framework Directive (MSFD), the EuroMarine workshop BIOZOO gathered European experts to evaluate the use of enzyme activities, oxidative stress markers, fatty acids, and stable isotopes for zooplankton-based assessments. Participants identified methodological priorities, including protocol standardization, inter-laboratory calibration, and baseline development, to ensure comparability across regions. This synthesis highlights how integrating biochemical and physiological biomarkers into existing monitoring frameworks can improve the detection of ecosystem responses to environmental pressures such as warming, pollution, and eutrophication. Strengthening biomarker applications in European Seas represents a step toward a more functional, harmonized, and responsive approach to pelagic habitats assessment.
The eastern Ionian Sea is an important area for marine fauna, but it is also a region of substantial overlap between human activities and natural ecosystem components. Using data from a fixed passive acoustic monitoring station deployed over a 7-month period (July 2022 - January 2023), this study describes the near-shore marine soundscape of northern Kefalonia Island and documents elevated noise levels associated with coastal and offshore anthropogenic activities. Underwater noise from recreational speedboats exhibited a prominent diel pattern during the summer months that was absent in winter. In contrast, diffuse low-frequency noise from offshore shipping traffic was persistent throughout the monitoring period. Additionally, offshore oil and gas seismic surveys conducted at the end of 2022 had a major acoustic footprint on the coastal soundscape. During the first two weeks of December 2022, sustained seismic airgun activity resulted in broadband (10-2000 Hz) received sound pressure levels of 114.4 dB re 1 mu Pa (Root-Mean-Square), with maximum daily zero-peak levels ranging from 140 to 147 dB re 1 mu Pa. Continuous soundscape monitoring in these waters is essential for informing underwater noise management and mitigation measures under the European Union Marine Strategy Framework Directive, particularly in light of ongoing hydrocarbon exploration efforts in the eastern Ionian Sea and the establishment of the Ionian National Marine Park, which is primarily aimed at the conservation of marine mammals.
The present study investigates alterations in the coastal area of the Acheloos deltaic complex (W. Greece) during the period 1945-2020 and the shoreline response to anticipated sea-level rise under various RCP scenarios. The authors used two methods of analysis: area measurement in non-linear sections of the coast, and longitudinal displacement of the coastline using DSAS. The future state of the coastal area analyzed by considering IPCC predictions, adjusted for local conditions. The results reveal severe erosion in the entire study area, reaching 250 m (similar to 3.4 m/yr) in places, mostly due to the diversion of the main Acheloos River channel, whereas coastal protection works constructed in the 90s have partially mitigated the erosional rate. The IPCC predictions for 2100 show a continuous shrinking of the delta by 10% to 20% of the present area, while under the most extreme climate scenario, deltaic area loss could reach 60%. Regardless of the prevailing scenario, it was estimated that for each 0.1 m of sea-level rise, the average land loss at the deltaic area is approximately 2.8 km(2).
Non-indigenous butterflyfishes (Chaetodontidae) are increasingly detected in the Mediterranean Sea, often through oppor- tunistic observations supported by photographs or video. Here we report the first confirmed Mediterranean record of the Pennant coralfish Heniochus acuminatus (Linnaeus, 1758), based on a specimen speared off Larnaka (Cyprus) in August 2018 and photo- graphed immediately after capture. We also provide six new Mediterranean occurrences of the Red Sea bannerfish Heniochus intermedius Steindachner, 1893, recorded between February 2021 and November 2025: three captures from Lebanon (two preserved as vouchers), and three additional individuals documented exclusively by underwater video from Italy, Cyprus and Greece, which are conservatively reported as Heniochus cf. intermedius. Finally, we compile and critically update published Mediterranean Heniochus records (n = 21), highlighting the growing contribution of citizen science and social media to the detection of conspic- uous tropical fishes, while emphasizing the need for evidence-based reporting when identifications rely solely on visual material. The spatial clustering of H. intermedius in the Levant is compatible with the presence of an established population, although the broader spatio-temporal pattern indicates multiple introduction events of Heniochus spp. into the basin.
The purple dye murex (Bolinus brandaris), a gastropod mollusc, is a resource of local importance within the Mediterranean Sea (Spain, France, Italy, Tunisia, Greece and Turkey). It is fished all along the Catalan coast (NW Mediterranean), although fishing is concentrated in the area of the Ebro River Delta, where it is caught with bottom trawl, boat dredge and trammel nets. In the last two decades, from 2002 to 2023, a steady decreasing trend along the Catalan coast has been observed in landings (92% reduction, from 240.5 to 19.8 t), daily catch per vessel (78% reduction, from 14.1 to 3.1 kg/day/vessel), and fishing effort (fishing days with the sale of purple dye murex at the auction; 63% reduction, from 17068 to 6400 days). The three types of fishing gear involved in the purple dye murex fishery operate on different fishing grounds at different depths, which implies that the purple dye murex is fished throughout its bathymetric distribution and size range. The boat dredge and bottom trawl hourly yields markedly declined by 69% and 40%, respectively, over the past six years. Immature and below-minimum landing size individuals represent an important proportion of the catch. Considering the presence of immature individuals in the catch, boat dredging is the most detrimental for the species. At present, the economic dependence of fleets on purple dye murex is very low (1.3% revenue from first sale at the auction). The results of the assessment indicate that the purple dye murex population in the Ebro Delta is depleted.
Ports constitute hot spots for the introduction of species transported by maritime shipping and are therefore important sites for biological monitoring. The current study investigated the marine fouling community in Abu-Qir Port, Alexandria, Egypt (south-eastern Mediterranean basin), using a modified rapid assessment technique (similar to 6 h of sampling effort). A total of 95 taxonomic units were collected (84 identified to species level), with Annelida and Crustacea being the most diverse groups, comprising 31.5% and 30.5% of the total number of recorded taxa, respectively. The amphipod Dulichiella fresnelii was recorded for the first time as a new non-indigenous species (NIS) in the Mediterranean Sea. Overall, 39 NIS, including one questionable species, were found, comprising approximately 41% of the total biodiversity, of which 10 constitute new records for the Egyptian Mediterranean fauna, including 2 Annelida (Polychaeta: Oenone fulgida and Syllis crassicirrata), 2 Bryozoa (Celleporaria brunnea and Tricellaria inopinata), 5 Crustacea (Amphipoda: Ampithoe bizseli, Caprella scaura, D. fresnelii, and Stenothoe georgiana; Isopoda: Paranthura japonica), and 1 Porifera (Paraleucilla magna). Studies on fouling communities in ports are strongly recommended in order to obtain a more comprehensive overview of NIS presence and abundance. Baseline assessments in ports are crucial for assessing the potential impacts of NIS in these environments and for evaluating invasion dynamics.
Submerged caves in the Mediterranean Sea are unique ecosystems, sustaining diverse benthic communities shaped by environmental gradients. This study focused on the Jubilee Shoals cave system in the eastern Mediterranean (Cyprus), providing a quantitative analysis of benthic community composition, spatial distribution across cave zones, and the influence of environmental factors. The data were collected using closed-circuit rebreathers; 341 photo quadrats were analysed with specialised software to assess biodiversity within this cave system. Overall, 59 sessile taxa were identified at different rank, with sponges comprising 33% of richness. Phototrophic species dominated the entrance zone, while sponges and other low-light-adapted organisms prevailed in the darker areas. Light availability significantly influenced community structure. A progressive decline in biotic coverage from entrance to dark zones and an increase in non-living substrates highlighted the environmental limitations of more remote cave sections. Detailed 2-D and 3-D mapping enhanced our understanding of the structural complexity of the cave and species distribution. These findings emphasise the ecological vulnerability of sea caves and highlight the need for focused conservation efforts. This study establishes a foundation for future ecological studies in deep marine cave systems.
The Tortonese's stingray (Dasyatis tortonesei Capap & eacute;, 1975) is a poorly understood species, likely endemic to the Mediterranean Sea, where its distribution remains inadequately resolved due to historical taxonomic uncertainty and misidentification with its closely related congeners. The present study reports the first well-documented records of D. tortonesei in the Adriatic Sea, based on six specimens collected during systematic field surveys off Vlor & euml;, Albania. All specimens were identified through a comprehensive assessment of diagnostic morphological features, and detailed biometric data are provided. Notably, one individual exhibited a fully healed traumatic loss of both the tail and stinging apparatus, suggesting a degree of resilience to sub-lethal injury. The present findings extend the range of D. tortonesei and establish a valuable baseline for future biodiversity assessments. In addition, this paper underscores the urgent need for integrative taxonomic approaches and regional capacity-building to improve species-level identification and inform effective conservation of Mediterranean elasmobranchs.
This paper presents the first study examining the relationship between angiosperms, their associated bivalves, and environmental conditions, with the aim of assessing the health of the El Mellah lagoon. The study was conducted monthly throughout 2019 at three stations selected for their continental and marine influences. The seagrass beds exhibit remarkable abundance, with biomass reaching up to 1313.32 +/- 132.73 g DW m-2 in September. The biomass of Zostera noltei is positively correlated with temperature, while that of Ruppia maritima is positively correlated with salinity. Bivalve density in El Mellah follows the variation in seagrass bed biomass. The densities of the native bivalve Loripes orbiculatus and the invasive species Arcuatula senhousia increase with both the aboveground and belowground biomass of Z. noltei, as well as with temperature. This suggests the existence of a tripartite mutualism between seagrass beds, lucinid bivalves, and their sulphide oxidising gill symbionts. These findings highlight the importance of investigating the factors influencing the mutualistic relationship between seagrasses and lucinid bivalves in the El Mellah lagoon, not only to improve the long-term success of seagrass restoration but also to strengthen their resilience to climate change.
This collective article presents new information about 18 species occurring in 12 Mediterranean countries from the Alboran Sea to the Levantine Sea. Five lessepsian species namely Erugosquilla massavensis, Syrnola fasciata, Plocamopherus ocellatus, Maritigrella fuscopunctata and Siganus javus have spread within 2025 to neighbouring MSFD areas. Another five are here reported as first country records [Polyandrocarpa zorritensis (Malta), Gonioinfradens giardi (Italy), Istiblennius meleagris (Egypt), Epinephelus fasciatus (Israel), Lophocladia trichoclados (Montenegro)]. Cladophora patentiramea has spread from the Levantine to the Aegean Sea, while Pinctada radiata has reached Granada, and C & aacute;diz. The Atlantic fish Enchelycore anatina and Synodus synodus have expanded their distribution to Montenegro and Syria respectively. Three rare native species are reported for first time at country level, while a fourth (Mobula birostris) has made an appearance more than a century after its first Mediterranean record.
