This study investigated the distribution, abundance, and population structure of the invasive Procambarus clarkii in understudied small marginal water bodies along the Venice lagoon. These water bodies comprise expanses of brackish water, shallow freshwater canals, and small ponds, previously constituting part of a fishing valley. The aim was to fill the knowledge gap about the species colonization of these specific environments, analyse its relationships with the aquatic fauna and evaluate whether it could also inhabit coastal environments with increasing salinities. Sampling was conducted using fishing pots in 10 stations, each characterized by distinct environmental characteristics such as salinity, nutrient concentrations, water body width, water flow and floristic cover. The results showed that P. clarkii successfully invaded most of these marginal habitats. Although poor water quality and high nutrient levels do not preclude the presence of this species, they seem to influence its abundance. In contrast, salinity resulted to be a primary factor determining the presence or absence of the species, acting as a physiological barrier, limiting P. clarkii expansion toward more sea-influenced parts of the lagoon coastal environments. Moreover, pH, while not affecting the presence of the species, resulted in affecting the growth rates of individuals. In terms of community dynamics, the native nektonic fauna appears largely replaced by more adaptable non-native species, with P. clarkii likely contributing to this displacement, alongside other impacts. Moreover, although strong direct associations with specific aquatic fauna are limited, evidence suggests reciprocal predation between crayfish and fish during different life stages.
Common bottlenose dolphins Tursiops truncatus have adapted to foraging and scavenging behind fishing trawlers in many areas around the world. This opportunistic behaviour is widespread in Adriatic Sea waters off the region of Veneto, Italy. On October 1st, 2020, we tracked a group of bottlenose dolphins from a 6 m boat, north-east of the Po River Delta. The dolphins foraged behind midwater pair trawlers, then four individuals abandoned the vessels and engaged in fast, highly-directional movement toward another distant pair of midwater trawlers, at speeds of 8-14 km/h, as the trawlers moved away from the dolphins. After 29 min of fast directional travelling, the dolphins reached the midwater trawlers and immediately started foraging in their wake. GPS tracking of dolphin positions, combined with trawler positions obtained from AIS data matching vessel name/plate, revealed that the trawlers were 2.6 km away from the dolphins when the animals first appeared to have detected them – consistent with reports of detection-and-approach in other seas. While bottlenose dolphins in our 3,000 km2 study area frequently moved from one fishing trawler (or pair of trawlers) to the next, the trawlers’ detection-and-approach event reported here was the longest observed during our 7-year study, totalling 721 encounters with fishing trawlers and 17,432 km of survey effort during 129 days of monitoring trawling activities. Longdistance detection can theoretically enhance foraging opportunities, though the substantial negative effects of trawling on marine ecosystems make it difficult to disentangle causes and effects, and determine whether there may be net demographic benefits to the dolphins.
The Mediterranean Sea is significantly impacted by non-indigenous species (NIS) that have arrived through various routes, most notably shipping traffic. As a result, commercial harbours have become critical hotspots for these introductions. The Libyan coastline, particularly in the vicinity of major ports, is highly vulnerable to the arrival of NIS. During a targeted assessment of heterobranch biodiversity conducted from 2023 to 2025, the cephalaspidean Tubulophilinopsis lineolata was documented for the first time in both Libya and the Mediterranean Sea. This discovery highlights the urgent need for increased monitoring and for the creation of systematic biodiversity inventories covering Libya’s understudied coastal regions.
This study investigates the influence of environmental parameters on the abundance, biomass, and spatial distribution of demersal elasmobranchs in the eastern Sea of Marmara over a ten-year period (2014–2024). Catch per unit effort (CPUE) data from bottom trawl surveys were combined with in situ measurements of dissolved oxygen, temperature, salinity and depth. Multivariate analyses indicate that dissolved oxygen and temperature are key factors associated with spatial variability of demersal elasmobranchs in the investigated area. Temporal patterns show an increase in their abundance until the late 2010s, followed by a marked decline, which may reflect increasing environmental stress as a cause of the decline. These findings suggest that ongoing deoxygenation, together with other environmental parameters, may play an important role in structuring demersal elasmobranch assemblages in the region.
The introduction of non-indigenous species (NIS) into the Mediterranean Sea represents a growing ecological concern, driven by multiple vectors including shipping, aquaculture, and climate-mediated range expansions. In this study, we report the first Mediterranean record of the Japanese amberjack Seriola quinqueradiata Temminck & Schlegel, 1845 (Carangidae), a species native to the northwestern Pacific Ocean. A specimen was captured by an angler on 13 February 2026 along the coast of Nardò (Ionian Sea, Italy), near Zone C of the Porto Cesareo Marine Protected Area. Species identification was confirmed through an integrative taxonomic approach combining morphological examination and mitochondrial COI gene barcoding. A second specimen, likely belonging to the same species, was captured shortly thereafter in the same area. The most plausible introduction pathways were discussed. This finding highlights the importance of continuous monitoring of marine biodiversity, particularly through the integration of citizen science and fisheries observations, which are essential for the early detection of rare and potentially invasive species.
The rapid colonisation of Maltese coastal waters by the non-indigenous Sepioteuthis lessoniana Lesson, 1831 is hereby documented through the ‘Spot the Alien’ citizen science campaign, to which a considerable number of catches and sightings of the species were submitted in rapid sequence over a three-month timeframe. The study also compares sea surface temperature values for the July-December period of 2015, 2020 and 2025 for the same waters, in order to explore the putative influence that sea temperatures might have on the observed rapid expansion of this non-indigenous species (NIS). The findings of this study highlight both the notable spread of the species across local waters and the important role of citizen science in early detection and monitoring of non-indigenous species.
The present study reports the first confirmed occurrence of the yellowbar angelfish Pomacanthus maculosus (Forsskål, 1775) in Hellenic waters, extending the known Mediterranean distribution of this West Indian Ocean species. A single adult specimen was collected by spearfishing on 15 October 2025 from shallow coastal waters off southern Crete. Identification was based on distinctive coloration patterns, morphological characteristics, and meristic counts. The habitat consisted of steep rocky substrates adjacent to sandy plains, aligning with the known ecological preferences of the species. Possible introduction pathways are examined, with aquarium release or escape and natural westward range expansion from established Levantine populations considered as non-exclusive scenarios. This record bridges an apparent distributional gap between eastern and central Mediterranean records, which may partly reflect limited detectability due to the species’ cryptic habits rather than true absence. The finding underscores the importance of Crete as a strategic monitoring area for detecting the arrival and potential spread of marine non-indigenous species within Hellenic waters. Continued surveillance is essential to assess establishment and potential ecological implications.
Non-native species represent one of the major threats to the preservation of Mediterranean biodiversity, as asignificant number of marine organisms colonize this region either by passing through the Suez Canal or via other vectors, such as marine traffic and ballast water. Fourteen non-native goby species have already been documented in the Mediterranean Sea, with their distribution currently being restricted to the Levantine Basin and Aegean Sea, in addition to a single record from the Ionian Sea. In contrast, no non-native species from this group have been recorded in the Adriatic Sea to date. This study documents both the first record and evidence of an established population of the darter goby ( Ctenogobius boleosoma ) in the southeastern Adriatic Sea (Montenegro), identified by genus and species diagnosis. Thirteen individuals were collected from the Jaz River between September and December 2025. The fin coloration pattern is described, including the unusual pectoral fin coloration for this species.
The basking shark ( Cetorhinus maximus ), an endangered filter-feeding elasmobranch, is subject to significant anthropogenic pressures in the Mediterranean Sea. Despite its ecological importance, data from the North African coast are limited. This study presents the first multi-decadal analysis (1990-2025) of C. maximus occurrences in the Algerian Basin (GSA 04). A robust dataset (N=27), compiled from fisheries records, direct sightings, and citizen science contributions (33.3% of records), was used to investigate the environmental drivers of its distribution. Statistical analyses revealed a significant increase in observation frequency since 2019 (Mann-Kendall τ=0.362, p<0.001). Occurrences exhibited a clear seasonal pattern, peaking in June. Bycatch accounted for the majority of records (63.0%), primarily associated with driftnet fisheries in the western sector. A strong positive correlation was found with sea surface temperature (Spearman’s ρ=0.68, p=0.021). In contrast, a negative relationship with primary productivity (ρ=-0.61, p=0.038) suggests a “trophic lag” whereby shark presence coincides with post-bloom conditions. Sea surface salinity (SSS) was not a significant predictor (ρ=0.12, p=0.45), indicating a broad tolerance to the hydrographic gradients of the Algerian Current. These findings highlight the Algerian coast as an important seasonal migratory corridor. The observed overlap between shark presence and intensive fishing activity underscores the urgent need for conservation measures. We recommend integrating citizen science into regional monitoring programs and implementing seasonal fishing gear restrictions to reduce bycatch mortality and support the long-term persistence of this species in the Mediterranean.
The non-indigenous green alga Caulerpa cylindracea is among the most invasive macroalgae in the Mediterranean Sea and has progressively expanded throughout the Adriatic basin since its first record in 2000. This study reports the first records of C. cylindracea in the Gulf of Trieste, the northernmost part of the Adriatic Sea. The species was first recorded in September 2022 at San Bartolomeo (Italy), where only a few thalli were recorded within a Cymodocea nodosa meadow. In September 2023, two thalli were recorded at Lazaret, representing the first record of the species along the Slovenian coast. Targeted surveys conducted between 2023 and 2025 documented the current spatial extent of the species at both sites and revealed an additional population at the Rex site, between the towns of Koper and Izola. At San Bartolomeo, C. cylindracea occupied an estimated 14,497 m² in July 2023 and 12,331 m² in September 2024. At Lazaret, the species occupied an estimated 12,114 m² by September 2025, while the newly recorded population at the Rex site, between the towns of Koper and Izola, covered approximately 3,000 m². Because the surveyed areas were not monitored systematically before the initial detections, these estimates represent the observed spatial extent of the populations at the time of each survey rather than a quantified rate of spread. These findings confirm the establishment of C. cylindracea in the Gulf of Trieste, extend its known distribution to the northernmost part of the Adriatic Sea, and provide a baseline for future monitoring and assessment of its ecological impacts in this environmentally heterogeneous coastal basin.
Saltmarsh restoration is widely implemented in the Venice lagoon, yet the extent to which different restoration designs influence benthic and epibenthic communities remains unclear. This study compares natural and artificial saltmarshes across two lagoon basins (central and northern), accounting for large-scale environmental gradients and local habitat characteristics. Benthic and epibenthic communities were analyzed in creeks. Basin-scale conditions, particularly salinity and sediment characteristics, emerged as the main drivers of community structure, with clear differences between lagoon sectors. The central basin supported more diverse and functionally heterogeneous assemblages, whereas northern sites showed lower diversity and were dominated by deposit feeders. The effects of restoration design were contextdependent. In the northern basin, artificial and natural saltmarshes hosted similar communities, while in the central basin, artificial marshes built with sandy sediments supported distinct assemblages compared to natural sites. Overall, while environmental gradients constrain community patterns, restoration design - especially sediment characteristics - can influence ecological trajectories, highlighting the need for site-specific restoration strategies.
Chondrichthyans are key components of marine ecosystems, playing an important role in the regulation and stability of coastal and offshore food webs. Despite their ecological relevance, many chondrichthyan species have experienced severe global decline, primarily driven by intense fishing pressure and bycatch. In this context, uncertainties regarding their historical and contemporary distribution limit robust evaluations of population trajectories and the magnitude of human impacts. In this study, we review and update the known distribution of the round stingray Taeniurops grabatus (Geoffroy Saint-Hilaire, 1817) in the Mediterranean Sea, reporting the presence of the species in ten Mediterranean countries, mainly along the southern and eastern basins. Furthermore, by combining historical knowledge and citizen science data, we provide the first documented records of T. grabatus from Spanish Mediterranean coastal waters and confirm both historical and recent occurrences in the southeastern Iberian Peninsula. By integrating historical with contemporary records obtained through citizen science, our study demonstrates the complementary value of these approaches to offer a more comprehensive understanding of the presence and temporal change of this rare species in the Mediterranean Sea.
The gold coral, Savalia savaglia , is generally considered a rare parasitic parazoanthid mainly found in the Mediterranean Sea, with occasional records in the Atlantic Ocean. Recently, more has come to light regarding its distribution patterns, genetic information, and habitat due to the increased research focus. Listed as ‘Near Threatened’ on the IUCN Red List, S. savaglia requires continued monitoring, and updated assessments of its distribution are crucial. Here, we compile recent data and current knowledge on this species, highlighting both confirmed findings and unresolved questions, like the question of possible cryptic species and obligatory parasitism. We also report new records from the eastern Adriatic Sea, helping to fill the existing gaps in the known distribution of the morphotype S. savaglia .
The smallscale codlet, Bregmaceros nectabanus Whitley, 1941, is a small gadiform fish native to the Indo-West Pacific and the Red Sea. It is considered non-indigenous in the Mediterranean Sea, with its first records appearing in the early 2000s. This paper reports the first confirmed occurrence of B. nectabanus in Montenegrin waters. The specimen was caught by beach seine in the interior of Boka Kotorska Bay at a depth of less than 20 m. Morphometric measurements were compared with existing Adriatic and Mediterranean records, revealing general consistency, although minor deviations were attributed to intraspecific variability, ontogeny, or ethanol-induced shrinkage. An updated overview of Mediterranean records from 2002 to 2024 is provided. While the overall distribution pattern supports a Lessepsian migration pathway, the occurrence of the species in areas of intensive maritime traffic suggests that secondary dispersal via ballast water may contribute to its spread. These findings extend the known range of B. nectabanus in the Adriatic Sea, indicating an ability to exploit shallow coastal environments. Further monitoring and genetic studies are recommended to clarify the mechanisms underlying its ongoing expansion.
Marine environments worldwide are affected by various anthropogenic activities, and many cetacean populations face increasing human pressures, especially those in coastal habitats. The key threats affecting common bottlenose dolphins (Tursiops truncatus) today are fishery interactions, prey depletion, habitat disturbance, pollution and climate change. The Mediterranean basin is one of the areas subjected to enormous pressure from human activities, in particular the Adriatic Sea, where bycatch represents the most frequent cause of dolphin mortality related to fisheries, followed by larynx strangulations, long-term tail entanglement and presence of fishing gear residue in the stomach. In this study, we present the first published case of a resident bottlenose dolphin from the Adriatic Sea population with a known observation history and confirmed cause of death observed in the Croatian part of the Adriatic Sea. By comparing the photographs of the dolphin's dorsal fin taken during the post mortem examination with those obtained from boat-based surveys, we were able to identify the individual L_1834, which has been observed since 2018 along the eastern coast of the northern Adriatic Sea. Over three decades of monitoring live bottlenose dolphins and their systematic mortality surveillance in Croatian waters enabled us to gain insight into the ranging and residency pattern of the dolphin stranded in 2023 due to larynx strangulation with fishing net parts.
Among the 64 native Mediterranean gobies (Gobiidae and Oxudercidae), a rather high number of species was historically considered rare, and until today, some of these species have only a limited number of published records with a positive identification. Reviewing published data and applying quantitative thresholds shows that out of the 64 native species, 25 remain rarely recorded and can be considered elusive. Additional 13 species had been considered rare historically or just a decade ago. However, the increasingly high number of publications on gobies since the turn of the century revealed that the latter ones now have to be considered rather common. Almost all elusive gobies appear to be restricted to northern and eastern Mediterranean areas. The four areas with the highest elusive species richness showed no clear biogeographic pattern. Rather, an increased diversity counts of elusive gobies are likely sampling artifact of a high level of research activity in these areas. Almost all elusive Mediterranean gobies are very small littoral fish with no recognizable general preference for a specific bottom habitat or depth range. The best available published source was used to review and discuss the rarity of Mediterranean fishes in general. However, most of the elusive and potentially rare Mediterranean fish species lack a review of all their positive published records that would allow quantified discussion and conclusion on their elusiveness.
Here we report the capture of a large female smooth-hound, Mustelus sp. off Corsica, France, measuring 189 cm TL, which exceeds the previously reported maximum size (170 cm TL) of this genus in the Mediterranean Sea. This specimen, as well as two others captured in Corsican waters, had remains of the invasive blue crab Callinectes sapidus in their stomachs. The paper provides preliminary insights into the foraging behaviour of Mustelus sp., suggesting a potential regulatory role in controlling the invasive blue crab in Mediterranean estuarine and lagoon ecosystems. If proven, these first aspects of foraging activity could be a strong argument to improve a more stringent conservation of the smooth-hounds in the Mediterranean Sea.
Bivalves deposit shell material during their lifetime, and many species’ growth patterns and age can be determined from their growth increments. Shell growth varies through ontogeny and can also have temporal and spatial variations dependent on the environmental conditions. Some scallop species (family Pectinidae) have clearly visible annual growth lines on the external surfaces of their shells that enable reliable analysis of growth patterns. Pecten jacobaeus , a commercially important scallop species that lives in Mediterranean coastal waters, is one of them. In this study, we analysed variations in growth and age of P. jacobaeus specimens collected from five locations in the eastern part of the Adriatic Sea. To obtain insights into spatial variations in feeding ecology, nitrogen and carbon isotopes were analysed in mussel tissues. Sampling was conducted in late 2023 and the first half of 2024, and between 45 and 60 specimens were collected at each location. In the northeast Adriatic (Istria), samples were collected by beam trawl fishing vessels, while at other locations (Iž, Maslenica, Prokljan, Pelješac) SCUBA divers were engaged. The shell length of analysed specimens varied from 44.6 to 149.5 mm, while their estimated age ranged from one to 12 years. The data on age and shell length were fitted to the von Bertalanffy growth function. Growth was also estimated using the Gulland-Holt plot, and a relative growth functions were constructed. Results of this study contribute to the understanding of P. jacobaeus growth dynamics and have potential applications in fisheries management and conservation.
Zooplankton plays a crucial role in marine ecosystems, serving as an important link between primary producers and higher trophic levels. This study investigates zooplankton community structure and distribution in the area influenced by physical phenomena of internal island-trapped waves (ITWs) in the southern Adriatic. To assess the responses of the different zooplankton groups to ITWs, high-frequency sampling was carried out in July 2022. The results revealed pronounced shifts in zooplankton community composition, with taxa such as Evadne spinifera , Oithona spp., and Paracalanus parvus parvus exhibiting the most dynamic responses to nanophytoplankton availability. Centropages typicus and Temora stylifera showed depth-specific distribution patterns, reflecting their feeding preferences for microphytoplankton and adaptability in food sources. Organisms such as tintinnids, copepod nauplii, and radiolarians responded strongly to ITWs, while Oikopleura longicauda responded with a time lag, suggesting complex trophic interactions influenced by both biological and physical factors. These findings highlight the response of zooplankton community structure to specific physical dynamics, which likely influence trophic interactions and may affect the efficiency of energy transfer in the pelagic food web. The study emphasises the importance of high frequency sampling for capturing the fine-scale ecological processes that determine zooplankton dynamics in physically dynamic environments.
The occurrence, growth, external morphology and reproductive phenology of a Gelidium adriaticum settlement from the midlittoral zone in St. Simon Bay (Slovenian coast, Gulf of Trieste, northern Adriatic Sea) were investigated. The study was based on monthly sampling conducted for one year, from January to December 2023. The studied settlement was well developed in shaded rock crevices, forming dense turfs with a very patchy and irregular distribution. It was characterized by a slight predominance of tetrasporic thalli, with a ratio between the three reproductive stages (tetrasporic:sterile: cystocarpic) of 1.19:1.04:1.00. The mean values of the morphological characteristics studied (height and width of the thallus, width of the widest part of the thallus axis, width of the apical, middle and basal parts of the erect axes) varied between seasons and reproductive stages. In general, these values were lower in the cystocarpic thalli than those in the tetrasporic and sterile stages in all seasons.
