The feeding ecology of sympatric elasmobranchs provides key insights into trophic interactions and species coexistence within demersal ecosystems. The current study examined the diet composition and trophic relationships of three skate species (Raja asterias, Raja clavata, and Raja miraletus) in the eastern Ionian Sea (central Mediterranean). Stomach content analysis was combined with quantitative dietary indices and multivariate statistical approaches, including NMDS, PERMANOVA, SIMPER, and Schoener’s overlap index. All skate species primarily consumed benthic crustaceans and demersal teleost fishes, although differences in prey contribution were detected among species. Raja clavata exhibited higher prey diversity, whereas R. asterias and R. miraletus showed stronger reliance on decapod crustaceans. Multivariate analyses revealed significant interspecific differences in diet composition with generally low-to-moderate trophic overlap among species. These findings suggest that sympatric Rajidae species exploit similar prey resources while maintaining partial trophic partitioning, possibly reducing direct niche overlap and facilitating ecological coexistence. This study contributes to the understanding of trophic structuring in Mediterranean skate assemblages and supports ecosystem-based approaches to demersal fisheries management.

Partitioning of the Mediterranean basin has so far mainly focused on surface waters, relying on biogeochemical and hydrological data while the Mediterranean seafloor has received much less attention. Bioregions are essential units for conservation planning, as they provide a framework for designing representative networks of protected areas. Therefore, seafloor-specific bioregions are needed to support the management and conservation of benthic ecosystems. While benthic habitat mapping is generally based on macrofaunal patterns, we propose the first mesoscale partitioning of the Mediterranean seabed based on epibenthic megainvertebrate communities. Benthic records from the MEDITS programme (International Mediterranean Bottom Trawl Survey) were used to partition the Mediterranean soft bottoms. Using k-means clustering combined with Random Forest modelling, we grouped sites according to similarities in biotic composition and predicted their distribution in relation to environmental variables. The analysis was conducted independently across four sub-basins: the Western Mediterranean, the Central Mediterranean, the Adriatic Sea, and the Aegean Sea. This approach identified 16 distinct bioregions, each characterized by unique epibenthic megainvertebrate communities. The partitioning revealed a pronounced bathymetric gradient, with deep-sea bioregions showing a more homogeneous set of indicator taxa and greater similarity across regions compared to the more distinct communities found on the shelf and slope. These coherent bioregions can serve as spatial units to enhance the representativeness of conservation priority networks and provide a valuable complement to the existing EUNIS seabed habitat classification, which does not explicitly account for vulnerable epibenthic megainvertebrate communities.

This study explores the impact of spatial management measures on bull ray (Aetomylaeus bovinus) bycatch in the eastern Ionian Sea (Central Mediterranean). Bottom trawlers and small-scale fisheries (SSF) interact with the critically endangered bull rays due to habitat/fishing ground overlap and gear susceptibility. Unlike bottom trawling, which is monitored through Vessel Monitoring Systems (VMS) in the study area, assessing bycatch risks in SSF is hindered by data limitations, including the lack of vessel positioning systems and limited records of bull ray bycatch. To address this, we employed an extended Multi-Criteria Decision Analysis method, alongside VMS analysis and species distribution models, to spatially estimate SSF and trawling effort and map bull ray habitats. The estimated fishing effort and other bio-economic parameters were used as input in a dynamic spatially explicit bio-economic model (DISPLACE) which was applied to simulate fishing effort re-distribution under the scenario of trawling ban in Marine Protected Areas and Natura 2000 sites, based on a national commitment linked with the EU Marine Action Plan provisions. Predicted fishing effort (current and re-distributed) and bull ray spatial distribution were then used as input in the Productivity-Susceptibility Analysis to estimate bycatch risk spatially. The predicted outcomes of the alternative scenario were compared with the baseline situation. Results revealed that the species is more abundant in the northern part of the study area where the highest bycatch risk is exhibited. The trawling ban in protected areas and effort displacement increased bycatch risk by +9% on average, mainly affecting the northern study area, while the central and southern areas remained unchanged. The approach followed aims to support the implementation of ecosystem-based fisheries management by informing on bycatch risks and highlights the need for developing a planning framework integrating multi-objective optimization in each social-ecological system.

Loligo vulgaris, a semelparous cephalopod of commercial importance is mainly considered as by-catch in the Mediterranean bottom trawl fishery without specific fisheries regulations. In this study, the overall size selection pattern for L. vulgaris was examined in the Mediterranean bottom trawl fishery. Specifically, the size dependent escape, discard, and landing probabilities were estimated for two seasons (summer and autumn) and for three codends of 40 mm diamond (40D), 40 mm square (40S) and 50 mm diamond meshes (50D). In addition, an exploitation indicator quantifying the efficiency of each codend and season in releasing or catching individuals below the length at first maturity (LFM) was estimated. The results showed that a large proportion of juveniles were retained in all codends and both seasons, limiting the spawning opportunities for this semelparous species. The 40D exhibited the lowest selectivity in both seasons. No differences were detected between the 40S and 50D codends during summer. The 40S was more appropriate in autumn, allowing more individuals below the LFM to escape. However, even in this case a large proportion of juveniles remained in the codend. Fisher selection behaviour revealed a low discard probability but a high presence of juveniles in the landings. These findings demonstrated that further improvement of the codend selectivity is needed to reduce the capture of L. vulgaris at sizes before its unique spawning. Nevertheless, this will result in substantial economic losses for fishers. Therefore, alternative management measures should be investigated to ensure the sustainable exploitation of the species in the Mediterranean.

The importance of healthy food has been emphasized by the EU Commission, highlighting seafood safety due to contaminant bioaccumulation in marine organisms. This study measured total mercury (THg), cadmium (Cd), and lead (Pb) concentrations in the soft tissue of five commercially important species (Lophius budegassa, Aristaeomorpha foliacea, Nephrops norvegicus, Parapenaeus longirostris, Illex coindetii) collected from Greek waters during the "MEDITS" survey. Results showed elevated THg levels in L. budegassa (0.85 +/- 0.59 mg/kg) and N. norvegicus (0.55 +/- 0.30 mg/kg), and Pb in I. coindetii (0.51 +/- 0.39 mg/kg), exceeding EU safety limits. Consumer health risk was evaluated for adults and children using estimated weekly intake (EWI) and target hazard quotient (THQ). The EWI for all metals surpassed the provisional tolerable weekly intake (PTWI) set by the European Food Safety Authority. THQs indicated potential health risks associated with consuming 3 kg/year of L. budegassa for adults, and 1 kg of L. budegassa, 3 kg of A. foliacea, and 2 kg of N. norvegicus for children. Therefore, it is recommended to consume seafood in specific proportions, ensuring a variety of species are included in the diet. Further research is needed on contaminant levels across all commercially relevant species from Greek waters.

Analysis of the temporal and spatial distribution of 686 records of egg masses and egg mass groups from (i) recreational divers and posted in the various public media, (ii) scientific survey data collected during research programs and (iii) publications in peer-reviewed literature plus published and unpublished information on the seasonality of the occurrence of mature females, demonstrated that the reproduction of Loligo squids occurs throughout the Lusitanian zoogeographical province all year round with varying seasonal peaks. This may be due to high phenotypic plasticity, with the life cycle adapting to local conditions, or the existence of small discrete stock units related to individual water features. In warmer and relatively productive waters the spawning peak is more extended, and percentage of mature females in catches is lower In the Mediterranean the peak of occurrence of both mature females and spawned eggs gradually shifts to earlier dates from the west to the east, which is consistent with respective changes of the earlier peak of productivity. There is little or no gap between peak of occurrence of mature females and peak of the egg mass records. Spawning grounds of L. vulgaris extend in the Mediterranean area much deeper than thought before and they extend from 3 m to 550 m. Egg masses were reported by recreational scuba divers from deeper locations in the central Mediterranean than in other areas. Loligo forbesii egg masses were found between 170 and 720 m.

The use of cephalopod beaks in ecological and population dynamics studies has allowed major advances of our knowledge on the role of cephalopods in marine ecosystems in the last 60 years. Since the 1960’s, with the pioneering research by Malcolm Clarke and colleagues, cephalopod beaks (also named jaws or mandibles) have been described to species level and their measurements have been shown to be related to cephalopod body size and mass, which permitted important information to be obtained on numerous biological and ecological aspects of cephalopods in marine ecosystems. In the last decade, a range of new techniques has been applied to cephalopod beaks, permitting new kinds of insight into cephalopod biology and ecology. The workshop on cephalopod beaks of the Cephalopod International Advisory Council Conference (Sesimbra, Portugal) in 2022 aimed to review the most recent scientific developments in this field and to identify future challenges, particularly in relation to taxonomy, age, growth, chemical composition (i.e., DNA, proteomics, stable isotopes, trace elements) and physical (i.e., structural) analyses. In terms of taxonomy, new techniques (e.g., 3D geometric morphometrics) for identifying cephalopods from their beaks are being developed with promising results, although the need for experts and reference collections of cephalopod beaks will continue. The use of beak microstructure for age and growth studies has been validated. Stable isotope analyses on beaks have proven to be an excellent technique to get valuable information on the ecology of cephalopods (namely habitat and trophic position). Trace element analyses is also possible using beaks, where concentrations are significantly lower than in other tissues (e.g., muscle, digestive gland, gills). Extracting DNA from beaks was only possible in one study so far. Protein analyses can also be made using cephalopod beaks. Future challenges in research using cephalopod beaks are also discussed.

European hake, Merluccius merluccius L. 1758, is a highly valuable demersal fish species exploited in both the east Atlantic and the Mediterranean Sea. Changes in the size-at-maturity of this species have been reported in various geographic areas. Size-at-maturity is a key parameter in fishery management. Our main goal was to study the trend of the size-at-maturity of European hake in the eastern Ionian Sea (Central Mediterranean) over the last five decades. Utilizing a multi-decadal series of data for various environmental variables, we employed multivariate analyses and non-additive modeling in an attempt to identify shifts in the climatic environment of the eastern Ionian Sea and whether the maturation of the hake population could be affected by these changes. The analyses used suggest a plausible environmental regime shift in the study area in the late 1990s/early 2000s. The decrease in size-at-maturity that was detected in the last two decades may, thus, be associated with environmental changes. However, as many fish stocks already experience fishery-induced evolution, further investigation is necessary to determine whether this environmental effect is an additional stressor on a possibly already fishery-impacted population. The outcomes of this study highlight the importance of investigating the relationship between fish reproductive traits and altered environmental conditions, as the latter are generally ignored during assessments, affecting the robustness of fishery management.

The veined squid, Loligo forbesii Steenstrup, 1856, occurs at the European Shelf areas including the Azores and represents a valuable resource for the European commercial fishery in the North East Atlantic. However, very little is known about its population structure and phylogeography. This lack of knowledge also impedes the development of sustainable fishery management for this species. The present study combined the use of two types of markers that retrieve patterns of gene flow in different time spans; the analysis of 16 nuclear microsatellites and sequencing of the mitochondrial cytochrome oxidase subunit I (COI). Whereas the high mutation rate of microsatellites allows the description of recent patterns of connectivity in species, the lower mutation rate of COI provides phylogeographic patterns on a longer timescale. A total of 347 individuals of L. forbesii were investigated from nearly the entire distribution range of the species, including the North East Atlantic Shelf, the Azores and the Mediterranean. Individuals from the Western and Eastern Mediterranean Sea have never been included in a genetic study before. We were able to analyse COI sequences from all 12 sampling areas and define three clades of L. forbesii. Due to our large sampling area, we are presenting 13 COI-haplotypes that were previously unknown. The microsatellite analysis does not include the Azores but three main clades could be identified at the remaining 11 sampling sites. Low F ST values indicate gene flow over large geographical distances. However, the genetically significant differences and an additional slight grouping in the microsatellite structure reveal that geographical barriers seem to influence the population structure and reduce gene flow. Furthermore, both markers provide strong evidence that the observed phylogeographic pattern reflects the geographical history of the Azores and the Mediterranean Sea.

Fisheries have important impacts on marine biodiversity. In this work, combined information on the abundance, species richness, diversity indices, species composition, trophic level and vulnerability index were examined for the first-time to detect differences in five units related to trawl fishing: the fish assemblage entering the trawl codend, and the escaping, retained, discarded and landed fractions, derived by the gear and fisher selection practices. The work was based on a case study conducted in the Mediterranean Sea, using three different meshes in the trawl codend (40mm-40D and 50mm-50D diamond meshes, and 40 mm-40S square meshes) and a cover of the codends with small mesh size. In general, trawl fishing produces an escaping fraction that was always lower in abundance, richness, and vulnerability index, similar in diversity indices and trophic level, and different in species composition compared to the fish assemblage entering the codend. In almost all cases, fishers selected as landings a fraction that was the lowest in diversity indices, and the highest in trophic level. In contrast, fishers discarded a fraction that was the highest in diversity and vulnerability index, and the lowest in trophic level. Although the three codends did not differ significantly in the fraction of escapees in terms of diversity indices, trophic level, and vulnerability index, the 40S codend showed a significantly higher percentage in the escaping number of species and individuals, and less differences in the species composition; in addition, lower percentage in abundance of discards and higher of landings in the retained catch (0.6:1) than did the other two codends (0.9:1). It was suggested that an urgent modification of the trawl for the elimination of the discarded highly vulnerable species (e.g. Elasmobranchs) is needed, and that trawl species-selectivity should be improved by allowing escape or avoiding catch of the discarded fraction to minimize biodiversity losses.

The European Union (EU) is one of the most important markets for cephalopods in the world. Currently, smallscale fisheries targeting the common octopus in the EU are of considerable social and economic importance, especially in southern European waters where more octopus are consumed as part of the traditional diet. Octopuses in Europe are excluded from quota regulations under the Common Fisheries Policy and EU Member States manage their fisheries employing different input and output control measures, especially in small-scale fisheries targeting the common octopus. The level of participation of the fishing industry in the management of their activity varies amongst Member States and some management arrangements in place are tailored at the local level. This manuscript focuses on four European countries with important small-scale artisanal common octopus fisheries (Portugal, Spain, Italy and Greece). It describes and compares the current status of small-scale common octopus fisheries in each country, their socioeconomic importance, the management arrangements in place, and the opportunities and challenges for their future. Despite the increasing importance of octopus fisheries in southern Europe, few countries have collected detailed data on the socioeconomic importance and management of these fisheries. The information provided contributes to increase the knowledge about the human dimensions of octopus fisheries in Europe.

Mediterranean coastal ecosystems provide various valuable ecosystem goods and services; however, they are vulnerable to ecological degradation due to a dramatic increase in resource use and environmental stress. Disentangling the effects of multiple human interventions on coastal ecosystems requires whole description of food web interactions using quantitative tools. A mass balance Ecopath model has been developed here for Saronikos Gulf, a naturally oligotrophic Mediterranean coastal ecosystem with a long history of human interventions. Our main focus was to describe the structure and functioning of the ecosystem, investigate the trophic interplay among the various compartments of the food web under the impact of mixed multi-gear fisheries, and to quantify resilience related emergent ecosystem properties. To this end, we reviewed a large amount of local and regional biological information which was integrated in 40 functional groups covering all trophic levels, while fishing activities were described with 7 fleets. The model shared characteristics of both productive (e.g., high amount of flows) and oligotrophic systems (e.g., low biomass accumulation) and presented typical features of Mediterranean ecosystem functioning, such as the importance of detritus as an energy source, strong benthic-pelagic coupling and the dominance of the pelagic compartment in terms of total production and consumption. Trophic forcing in the ecosystem of Saronikos Gulf was complex with both top-down and bottom-up drivers being important. Zooplankton was the central nexus between basal resources and higher trophic levels, while top predators such as hake, squids and anglerfish were identified as keystone species presenting a significant overall effect on the food web via direct and indirect trophic interactions. Ecological indicators depicted a moderately complex food-web of a large and immature ecosystem with its strengths in reserve being affected by environmental degradation. Additionally, exploitation indices classified fishing activities in Saronikos Gulf as unsustainable, affecting several target groups, including high trophic level species. However, the morphological and bathymetric complexity of Saronikos Gulf seems to function as a natural ecological reserve for the ecosystem by providing nursery grounds to various species (e.g., hake, small pelagic fishes) and supporting important fish stocks for local fisheries.

Shipping is the greatest pathway of non-indigenous species (NIS) introductions, and port areas are considered as alien hotspots. In this study, we analyzed data covering a 112-year period and found that Saronikos Gulf in Greece, hosting one of the largest container port terminals in Europe, is a hotspot of MS introductions. To date, 89 MS have been recorded, of which 8 are characterized as invasive. Most species belong to the taxonomic group of Mollusca (33%), followed by Pisces (22%). For the first time in the Mediterranean Sea, we report the presence of the micromolluscs Sinezona plicata (Hedley, 1899) and Ringicula sp. Moreover, we provide evidence for the trend of NIS introduction in the Saronikos Gulf across the past 70 years, the pathways of introduction and their importance through time, as well as the distribution of the most invasive species in the Saronikos Gulf. The information provided herein can assist the implementation of the EU Marine Strategy Framework Directive and inform MS management. As Transport-Stowaway remains the main pathway of NIS introduction in the Saronikos Gulf, our principal recommendation is to reinforce regulations for the adoption of better antifouling practices and more effective ballast water treatment and management.

The present study provides updated information on the occurrence, abundance and biomass distribution patterns and length frequencies of Merluccius merluccius in the Mediterranean Sea, by analysing a time series of data from the Mediterranean International Trawl Surveys (MEDITS) from 1994 to 2015. The highest values of abundance and biomass were observed in the Sardinian Seas. The use of a generalized additive model, in which standardized biomass indices (kg km–2) were analysed as a function of environmental variables, explained how ecological factors could affect the spatio-temporal distribution of European hake biomass in the basin. High biomass levels predicted by the model were observed especially at 200 m depth and between 14°C and 18°C, highlighting the preference of the species for colder waters. A strong reduction of biomass was observed since the year 2009, probably due to the strengthening of the seasonal thermocline that had greatly reduced the availability of food. The general decrease in biomass of several stocks of anchovy and sardine, preys of European hake, might be indirectly connected to the decreasing biomass detected in the present study. The length analysis shows median values lower than 200 mm total length of most of the investigated areas.

Letizia Sion 1, Walter Zupa 2, Crescenza Calculli 3, Germana Garofalo 4, Manuel Hidalgo 5,13, Angélique Jadaud 6, Evgenia Lefkaditou 7, Alessandro Ligas 8, Panagiota Peristeraki 9,10, Isabella Bitetto 2, Francesca Capezzuto 1, Roberto Carlucci 1, Antonio Esteban 11, Cristina Follesa 12, Beatriz Guijarro 13, Zdravko Ikica 14, Igor Isajlovic 15, Giuseppe Lembo 2, Chiara Manfredi 16, José Luis Pérez 13, Cristina Porcu 12, Ioannis Thasitis 17, George Tserpes 18, Pierluigi Carbonara 2

The Mediterranean Sea shows a trend of increasing temperature and decreasing productivity from the western to the eastern basin. In this work we investigate whether this trend is reflected in the cephalopod assemblages found throughout the Mediterranean. Data obtained with bottom trawl surveys carried out during the last 22 years by EU Mediterranean countries were used. In addition to analysing spatial differences in cephalopod assemblages, we also analysed putative temporal changes during the last two decades. For this purpose. the basin was spatially divided into bioregions. the trawling grounds were subdivided into depth strata, and the dataset was split into two time series of 11 years each. All analyses were done using PRIMER software. The species richness did not vary with the longitudinal gradient, though in most bioregions it showed a mild decrease with depth before plummeting in the deepest waters. Cluster analysis revealed four different bathymetric assemblages in all bioregions. Despite the contrasting conditions between basins and the claims of biodiversity loss, our study revealed that spatial and temporal differences during the last two decades were restricted to changes in the relative abundance of species from a common pool of species inhabiting the whole Mediterranean.

The kitefin shark Dalatias licha is a deep sea shark rarely recorded in the eastern Mediterranean Sea, where it has been incidentally caught by deep waters long-lines and trawling. The present study concerns a female of 99 cm in total length stranded on a Greek coast (SE Ionian Sea). It was found severely decomposed. Basic morphological measures were recorded and its stomach was removed for diet examination. The current work provides for the first time valuable biological information on this rare deep sea shark and new records of prey preference in the Mediterranean Sea.

Data on life history aspects of two species of Squalus genus were collated from five different studies carried out in the Eastern Ionian Sea from 1995 to 2014. Data were collected from 948 longnose spurdogs Squalus blainville (Risso, 1827) and 65 spiny dogfish Squalus acanthias Linnaeus, 1758 caught by trawl and longlines. The mean length of both species increased with depth. Sexual segregation was observed for S. blainville, whereas a segregation of immature and mature individuals was detected for S. acanthias. The length–weight relationship for S. blainville indicated positive allometry (b > 3) for both sexes, whereas a negative allometry (b < 3) was found for S. acanthias for the combined sexes. The sex ratio of both species was in favour of males. For S. blainville, the gonadosomatic and hepatosomatic indices differed significantly between sexes but not between seasons with the maturity data supporting the hypothesis of continuous reproduction throughout the year. Length at first maturity (L50) for female and male S. blainville was 603 and 413 mm respectively. For S. acanthias, males collected in autumn had finished their spawning activity; the single specimen caught in summer was reproductively active. Females, caught only in summer, were all gravid. Prey identified in the stomachs of S. blainville belonged to three major groups: fish, cephalopods and shrimps. Other groups such as echinoderms and ascidians were also found. Identified prey in the stomachs of S. acanthias belonged to two main groups, fish and cephalopods, although other groups (including echinoderms and polychaetes) were also present.