Greek Waters Research Articles

Evaluating the Sustainability of an Eastern Mediterranean Gillnet Fishery Based on the Catches of Undersized Individuals and the Reproductive Period of Targeted Species

The catch composition of a coastal gillnet fishery in the Eastern Mediterranean Sea was analyzed through a two-year experimental fishing survey. Seven fish species occurred regularly in the hauls. Surmullet, Mullus surmuletus, which is the most valuable demersal fish in Greek waters and the intended target of the gillnets in small-scale fisheries, was the most abundant and systematically caught species. Almost all surmullets were larger than their minimum conservation reference size. However, three commercially exploited species (Diplodus annularis, Pagellus acarne, and P. erythrinus) were caught systematically as undersized individuals. In addition, these three species were caught mostly as immature individuals. Moreover, the operational season of the surveyed métier overlapped completely with the reproductive period of five commercially exploited species (D. annularis, M. barbatus, M. surmuletus, Sphyraena sphyraena, and Trachurus trachurus). Improvements and the establishment of additional technical measurements should be considered for the small-scale gillnet fisheries in the studied area to attenuate their detrimental effects and achieve a better compromise between sustainable exploitation of the local multi-species fish resources and the need for an economically sustainable practice.

Diversity of Fish and Decapod Fry in the Coastal Zone of Amvrakikos Gulf

Amvrakikos Gulf and its surrounding coastal lagoons are of primary importance for the local biodiversity and fishing activities. Fish species inhabited the coastal lagoons based on the seasonal ongoing migration movements of fry and adult fish individuals from the sea towards the lagoons. Information on the early stages of fish and decapod species in the Amvrakikos Gulf is limited only to the planktonic ontogenetic stages and reproduction biology, respectively. The aim of this study was to describe the spatial distribution of fry from commercially important fish and decapod species in the coastal zone of Amvrakikos Gulf. The seasonal appearance of the early stage of the most commercially important fish species caught in the coastal zone of the gulf ranged from one to four seasons, depending on the species. Individuals of all ontogenetic stages (fry, juveniles, and adults) were reported for several species (A. boyeri, A. fasciatus, S. abaster, S. tyfle, and B. ocellaris), indicating that these species may be regarded as residents in the coastal zone, providing habitats for their entire life cycle. The average relative abundance of the species/genera exhibited no differences compared to other Greek brackish waters. The species composition in the Amvrakikos Gulf at 10 cm and above was in agreement with the transitional nature of the area, with permanent and occasional species present. The present study emphasizes the importance of the coastal zone as a nursery habitat for commercially important species.

New kid in town: Pinna rudis spreads in the eastern Mediterranean

In the Mediterranean Sea, the genus Pinna encompasses two large fan-shaped bivalve species, Pinna nobilis and Pinna rudis. Historically, both species coexisted in the western Mediterranean until a mass mortality event (MME) brought P. nobilis to the brink of extinction. Notably, P. rudis remained unaffected by the MME, and its recent successful recruitment and further spread have been hypothesized to be linked to the local extinction of P. nobilis. Although P. rudis has been sparsely recorded in the eastern Mediterranean Sea (with some of these records being doubtful), reports emerging in the summer of 2023 from researchers and citizens have unveiled its sudden spread in the region. This study documents the recent presence of P. rudis within Greek waters through a dedicated survey and molecularly confirmation through two distinct molecular methods. Information derived from a citizen science initiative, following photo-identification of the species was also included. Furthermore, an updated review of the distribution of P. rudis in the Mediterranean Sea, integrating data from literature and online repositories is provided. This research confirms the recent spread of P. rudis in Crete, the Greek Ionian Sea, and Cyprus (first verified records of the species in the regions), in marine areas where P. nobilis has become extinct, further strengthening the hypothesis that P. rudis has benefited from the collapse of P. nobilis populations.

An Economic View on the Effects of Invasive Rabbitfishes Based on Fishers’ Perspectives: The Case of the Parrotfish Métier in the South Ionian Sea

The effect of thermophilic species invasion in the eastern Mediterranean is well-noted in the literature. During the last decade in western Greek waters, small-scale fisheries (SSF) catches exhibit increased relative contribution of rabbitfishes, which have originated from the Red Sea and inhabited the country’s southeastern part since the Second World War. This study has used quantitative and qualitative information to assess the short-term economic effect of the rabbitfishes’ expansion in the SSF métier targeting the indigenous thermophilic parrotfish in the South Ionian Sea. The short-term micro-level negative economic effects of the rabbitfishes’ invasion and the corresponding adverse effects on fishers’ economic wealth have been estimated. The results indicate attitudinal differences among fishers, although their local ecological knowledge may enable them to avoid rabbitfishes’ hot spots and mitigate the respective economic losses, that particularly for smaller SSF vessels already seem to be quite important. As climate warming may further facilitate the expansion of rabbitfishes, outcompeting parrotfish, the latter métier may eventually become economically unsustainable. Fine-scale analysis at the métier level enables addressing the specificities of social-ecological systems and can contribute to informed and more effective decision making related to SSF, which is an important building block of Mediterranean coastal communities.

Risk assessment of Golani’s round herring (Etrumeus golanii) in the Greek seas (northeastern Mediterranean Sea)

Greek waters are the recipient of several alien species, mainly through natural dispersal following invasion and establishment of non-indigenous species (NIS) in neighboring areas, making their monitoring and mitigating their effects of paramount importance. The European Union legislation framework toward alien species invasions considers risk assessments as the top of the spear for a first assessment of NIS and their potential to become invasive or not. The Union List has already included top priority species, with very few marine species. Golani’s round herring (Etrumeus golanii) is a species of round herrings in the family Dussumieriidae, a Lessepsian migrant and belonging to a group of NIS in the Mediterranean basin that are less studied. Its distribution range is mainly limited in the southeastern Mediterranean Sea, while in the Greek seas, it has not yet been observed in the north Aegean and Ionian seas, probably due to temperature and oceanographical reasons. Its presence in the basin is recorded by commercial fisheries landings in several countries (especially purse-seiners), indicating a potentially positive effect on commercial fisheries. A risk assessment of E. golanii in Greek waters was carried out in this work, based on the Risk Assessment Scheme developed by the GB Non-Native Species Secretariat (GB Non-Native Risk Assessment—GBNNRA). An overall semi-quantitative summary of risk, in terms of likelihood of events and magnitude of impacts, was facilitated for several attributors, including confidence levels for each one. The assessment highlighted a very likely possibility of introduction in the Greek seas from neighboring countries, as well as successful establishments of populations with high confidence levels. A moderate magnitude of impact regarding its further spread was deemed, while a minor one was indicated in terms of native species pressure and a minimal one in terms of economic costs and public health. Overall, E. golanii was not characterized as an invasive alien species (IAS) and local communities could benefit from its presence (commercial fisheries); however, further studies focusing on its reproduction and spawning grounds should be implemented.

Hellenic karst waters: geogenic and anthropogenic processes affecting their geochemistry and quality

Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (< 100 mg L−1) and high-chloride content (> 100 mg L−1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L−1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.).

Invading the Greek Seas: Spatiotemporal Patterns of Marine Impactful Alien and Cryptogenic Species

The Greek Seas are greatly exposed to the proliferation of marine alien species. At least 242 alien species have been reported within Greek territorial waters, three-quarters of which are considered established, while their rate of introduction is increasing. Some of these species exhibit high invasiveness, imposing severe impacts on native ecosystems and ecosystem services. The spatiotemporal proliferation of these species outside their natural boundaries depends on several parameters, including their biological characteristics, native distribution range, introduction pathway, and time of initial introduction. Knowing the current and potential alien species distribution is essential for the implementation of effective management actions. To investigate the distribution of impactful cryptogenic and alien species (ICAS) in the Greek Seas, we combined all records available until the end of 2020 from eight types of data sources: (1) scientific literature, (2) grey literature, (3) offline databases, (4) online scientific databases, (5) personal observations of independent researchers, (6) communications with divers and diving centers, (7) in situ underwater sampling, and (8) social networks. The results of 5478 georeferenced records refer to 60 marine ICAS belonging to 16 taxonomic groups. The number of records and the overall number of ICAS present an increasing trend from the northern to the southern parts of our study area, and there is a clear distinction in community composition between the northern and southern subregions. This latitudinal gradient is mainly due to the large number of thermophilous Lessepsian species of West Indo-Pacific origin, which reach the southern parts of the study area through unaided dispersal. On the other hand, transport stowaways appear to be more prevalent in areas located near large ports, which show significant differences in ICAS numbers and community composition compared to sites located far from ports. Most records (&gt;40% of the total) were associated with rocky reefs, partly reflecting the preference of divers for this habitat type but also the presence of conspicuous, reef-associated impactful fish. The number of published records, as well as the number of reported ICAS, shows a dramatic increase with time, highlighting the urgent need for immediate proactive management actions and scientifically informed control measures.

Tracing Patterns and Biodiversity Aspects of the Overlooked Skates and Rays (Subclass Elasmobranchii, Superorder Batoidea) in Greece

Species belonging to the superorder Batoidea have been poorly assessed due to the lack of information on their life history aspects and their limited economic value. This work presents an overview of skates and rays inhabiting the marine Greek waters and reports biodiversity issues requiring resolution for conservation purposes. Overall, 30 species from nine families and 16 genera have been documented within the past 22 years, based on the available literature and technical reports from research surveys of the Hellenic Centre for Marine Research (HCMR). However, 28 species are currently confirmed, since the presence of two rajids has not been sufficiently demonstrated and hence is considered as doubtful. Recent changes in nomenclature allowed us to replace old with new names in four species on the Greek list; patterns in the frequency of occurrence were observed and species were assigned into five categories; and diversity and misidentification issues were reported by family. Although Greek waters are oligotrophic and not considered a biodiversity hot spot for elasmobranchs, a high number of batoid species is documented in the area; therefore, the need to reinforce knowledge on biological aspects of skates and rays, define their status and identify their main threats is essential.

Different Interspecies Demographic Histories within the Same Locality: A Case Study of Sea Cucumbers, Cuttlefish and Clams in Greek Waters

Coalescent methods in population genetics aim to detect biodiversity patterns, evolutionary mechanisms, and signatures of historical changes in effective population sizes with respect to the species fidelity. Restriction site-associated DNA sequencing (RADseq) was used to evaluate the population dynamics of invertebrate species within the same localities. New sequencing technologies, such as the ones employed by population genetics, could be used to improve the management and sustainability of marine and aquaculture resources. Sea cucumbers (Holothuria tubolosa) showed genetic differentiation patterns favoring limited gene flow between studied areas. Similar results for clams (Venus verrucosa) suggest local adaptation and low-dispersal abilities for sessile organisms. On the contrary, cuttlefish (Sepia officinalis) exhibited a panmictic pattern, resulting in a single genetic stock in the area. The larvae settlement duration may be responsible for such interspecies variations. Interspecies demographic modeling revealed different environmental pressures of historical events’ signatures with respect to the three invertebrates. Sea cucumbers favor a post-glacial bottleneck event followed by a more recent recovery, whereas cuttlefish favor an expansion before the late glacial maximum. Lastly, clams showed a constant effective population size in the area. The results of historical demographic changes in natural populations provide opportunities for critical evaluation and management in terms of the conservation of the species in the area.

Trace elements in edible tissues of elasmobranchs from the North Aegean Sea (Eastern Mediterranean) and potential risks from consumption.

Trace elements have the potential to bioaccumulate in marine organisms and to biomagnify towards the upper levels of marine trophic webs, resulting in a range of negative effects on organisms. Elasmobranchs are highly susceptible to bioaccumulation of trace metals, while their consumption by humans is increasing worldwide. Therefore, it is important to monitor the trace metal content in the edible tissues of elasmobranchs. This work reveals the content of 12 trace metals in the edible tissues of 10 elasmobranch species caught in Greek waters. Levels above the permissible limits for Hg and Pb were found in some species, while analysis of the lifetime consumption risk for adults and children using the Target Hazard Quotient (THQ), revealed a high risk for two of the most toxic substances on the priority list for substances, namely As and Hg. These are preliminary results, and further research is required to understand better the issue.

An Updated Greek National Checklist of Chondrichthyans

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”.

Review of Harmful Algal Blooms in the Coastal Mediterranean Sea, with a Focus on Greek Waters

Anthropogenic marine eutrophication has been recognized as one of the major threats to aquatic ecosystem health. In recent years, eutrophication phenomena, prompted by global warming and population increase, have stimulated the proliferation of potentially harmful algal taxa resulting in the prevalence of frequent and intense harmful algal blooms (HABs) in coastal areas. Numerous coastal areas of the Mediterranean Sea (MS) are under environmental pressures arising from human activities that are driving ecosystem degradation and resulting in the increase of the supply of nutrient inputs. In this review, we aim to present the recent situation regarding the appearance of HABs in Mediterranean coastal areas linked to anthropogenic eutrophication, to highlight the features and particularities of the MS, and to summarize the harmful phytoplankton outbreaks along the length of coastal areas of many localities. Furthermore, we focus on HABs documented in Greek coastal areas according to the causative algal species, the period of occurrence, and the induced damage in human and ecosystem health. The occurrence of eutrophication-induced HAB incidents during the past two decades is emphasized.

Crisis and Differentiation in the CFSP: Leaders, Laggards and Critical Junctures

This article explores the relationship between exogenous crises and internal, formal differentiated integration in the European Union (EU) maritime foreign and security policy. Drawing on institutionalist concepts and the analytical framework in the Introduction, we argue that crises may serve as drivers of uniform rather than differentiated integration in policy areas dominated by dissent or differing needs and interests. Specifically, crises mark ‘critical junctures’ that open windows of opportunity for EU integration supporters (‘leaders’) to convince reluctant states (‘laggards’ and ‘disruptors’) to pursue further integration. To substantiate these theoretical assumptions, the article explores two case studies of integration where Member States were unlikely to agree to joint measures. The first case examines the launch of the EU anti-smuggling mission EUNAVFOR MED Sophia in response to the refugee crisis in the Mediterranean, while the second case looks at the EU’s joint actions against Turkish natural gas exploitation in Greek and Cypriot sovereign waters. Both cases use process tracing to show how, in the face of exogenous crises, ‘leaders’ in maritime foreign and security policy successfully exploited windows of opportunity to persuade formerly reluctant EU Member States to adopt common measures (This article is an output of the EUFLEX project, which has been funded by the Research Council of Norway, project number 287131). crisis, differentiated integration, European Union (EU), leaders, laggards, maritime security policies, institutionalism

Non-indigenous freshwater fish research in Greece: Current status and future prospects

Many studies around the globe have documented that the introduction of non-indigenous fish species (NIFS) may pose severe impacts on native biota, ecosystem functioning, and ecosystem services. In Greece, publications on NIFS have increased in recent decades, however, review studies of past and current scientific research on freshwater NIFS in the country are currently lacking. Τhe aim of the present study was to: (a) assess the current state of knowledge of freshwater NIFS in Greece based on the existing scientific literature, (b) evaluate well-studied areas of NIFS research, and (c) identify important gaps that may direct national authorities to implement appropriate research, management and conservation actions reversing the negative impacts of NIFS. A systematic literature review on NIFS research within Greek inland waters was performed by applying the PRISMA methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Overall, our initial search resulted in 2,794 published articles, 87 of which met our selection criteria and were thus included for full analysis. Evidently, NIFS failed to attract the interest of ecologists in Greece until the turn of the century, at which point, publications increased at a rapid rate. However, the majority of the studies were mainly monothematic concerning NIFS distribution within freshwater ecosystems of Greece (37%), followed by studies on ecological and biological aspects of NIFS (28%). Studies based on fieldwork and laboratory experiments were by far the most common type of research, followed by studies based on bibliographic data. Despite the fact that almost half of the publications were field observational studies, most of them used only qualitative data (plain presence/absence data). Critical aspects of impact assessment were missing; 84% of the reviewed studies did not provide any concrete evidence of NIFS impacts to native biota. Overall, the focus of the studies was uneven, with important gaps in areas of theoretical and practical importance for policy-relevant detection, control, and management of NIFS. Findings may assist researchers in filling scientific gaps identified by our review and guide authorities to define national priorities to prevent and control the spread of NIFS within the country.

Rarely Reported Cryptobenthic Fish in Marine Caves of the Eastern Mediterranean Sea

Data on the distribution and ecology of cryptobenthic fish of marine caves in the Mediterranean Sea are extremely scarce but necessary for scientists and marine managers alike in order to understand these fish’s ecological role and assess their conservation status. Broadscale surveys by implementing underwater visual census and photographic sampling in marine caves of the northeastern Mediterranean Sea, within different expeditions during the last 5 years, brought to light new records of eight rarely reported cryptobenthic fish species. To a smaller extent, complementary citizen science data from diving professionals of Crete were used to fill distribution gaps. A total of 36 new records (66 individuals) from 18 marine caves and caverns of the Aegean and northeastern Levantine Seas were assembled, belonging to the gobies Corcyrogobius liechtensteini, Didogobius splechtnai, Gammogobius steinitzi, and Thorogobius ephippiatus, the blenny Microlipophrys nigriceps, the tripterygiid Tripterygion melanurum, the speleophilic bythitid Grammonus ater, and the gobiesocid Lepadogaster cf. lepadogaster. The above species have been rarely reported from the Eastern Mediterranean Sea, with D. splechtnai and G. steinitzi being recorded for the first and second time from Greek waters, respectively, while L. cf. lepadogaster constitutes the second record of a clingfish species in a marine cave of the Aegean Sea. Interesting behavioral and ecological habits were also noted for some species, based on in situ observations and photographic evidence. Our study contributes to filling gaps in the knowledge of cave fish diversity and demonstrates that cryptobenthic mobile species in understudied cryptic habitats are more common than previously thought in the Mediterranean Sea.

Biological aspects, population and fishery dynamics of the non-indigenous pearl oyster Pinctada imbricata radiata (Leach, 1814) in the Eastern Mediterranean

The pearl oyster Pinctada imbricata radiata (Leach, 1814) is considered as an invasive species and despite its presence, for more than half of a century in the Mediterranean its fisheries in Greek waters is illegal, unregulated and unreported (IUU) due to lack of legal framework and fisheries exploitation. The present study is based on a three-level approach including a(n): (a) in-situ field sampling of live shell specimens, (b) estimation of biological and population parameters and (c) estimate of population stock state complemented with in-depth interviews conducted to fishers. The specimens of the pearl oyster were collected from two enclosed gulfs in Greek waters from November 2018 to October 2019. Asymptotic lengths (L∝) were estimated at 100.63 mm and 103.04 mm, in the North Evoikos and Saronikos Gulfs, respectively and the growth coefficient (K) was estimated at 0.47 year −1 and 0.34 year −1, respectively. The longevity of the species was estimated at 5 years. Total mortality coefficients (Z) were 1.92 year −1 and 1.44 year −1, in the two areas, respectively and the exploitation levels (E) were computed as 0.68 year −1 and 0.65 year −1, respectively. The results of the present study will fill the gaps in knowledge of pearl oyster to set up a reference base for its exploitation as a fishery resource based on invasive species.

IMPACT OF TURKISH MILITARY OPERATIONS ABROAD ON THE FALL OF THE LIRA

In this study, the impact of military operations on the exchange rate is estimated. In particular, this study focuses on military operations in Turkey and its impact on the Turkish lira against the pound sterling. Therefore, the aim of the present study is to investigate the impact of Turkish military operations abroad on the fall of the lira. The purpose of this study is analytical-descriptive and theoretical studies. The results of the present study indicate that Turkey has direct, proxy or tension military operations in Libya, Syria, Iraq, Nagorno-Karabakh and Greek waters, which have a negative effect on the country's relations with the European Union and the United States, leading to a fall in value. The Turkish lira.

Taxonomic composition and assemblage structure of brachiopods from two submarine caves in the Aegean Sea, Eastern Mediterranean

Brachiopods exhibit a particular preference for cryptic habitats such as submarine caves. However, their assemblages have rarely been investigated quantitatively in this habitat. In this work, brachiopod assemblages were studied in detail for the first time in two Aegean submarine caves, Fara and Agios Vasilios, Lesvos Island, Eastern Mediterranean Sea. Six species of Recent brachiopods, i.e. Novocrania turbinata (Poli, 1795), Tethyrhynchia mediterranea Logan, 1994, Megathiris detruncata (Gmelin, 1791), Argyrotheca cuneata (Risso, 1826), A. cistellula (Searles–Wood, 1841), and Joania cordata (Risso, 1826), have been identified. The cave-exclusive species Tethyrhynchia mediterranea is reported for the first time from the Aegean Sea and Greek waters, increasing the regional brachiopod fauna to 13 species, and for the second time in the Eastern Mediterranean. Five species were present in both caves while T. mediterranea was found only in the internal dark ceilings and walls of Fara cave. In both caves the dominant species was Argyrotheca cuneata. Abundance and diversity increased towards the internal dark ceilings of both caves, which harboured a well-differentiated brachiopod assemblage compared to that of the outer cave zones.

Additional Records of Tripletail Lobotes surinamensis (Bloch, 1790), from the Eastern Mediterranean

In the Mediterranean Sea, Lobotes surinamensis (Bloch, 1790) is considered as a rare species, albeit an increasing number of individual-based sightings published in the literature. In this study, we present 32 additional records of this thermophilic species from the Greek and Cypriot waters; reinforcing the evidence that the species is becoming more common to the region. All of the records were collected as part of the citizen science project “Is it Alien to you? Share it!!!” by a participatory process involving fishers and taxonomic experts. This work highlights the important role of citizen science as a tool for public engagement and for monitoring species distribution in a changing environment, like the Mediterranean basin.

Length-Weight Relationships of 31 Fish and Invertebrate Species in the Northern Aegean Sea (Eastern Mediterranean Sea)

The purpose of this study was to examine the length-weight relationships (LWR) of fish and invertebrate species exploited by the small-scale coastal fleet in the northern Aegean Sea (eastern Mediterranean Sea). Length and weight measurements were collected during experimental trials carried out seasonally from April 2016 to February 2017. A total of 4358 individuals from 31 species (28 fishes, 2 crustaceans and 1 cephalopod) representing 21 families were collected. With the exception of brown comber (Serranus hepatus) and rough ray (Raja radula), all LWR slopes fall within the 2.5 to 3.5 range. The median b value for fishes was 3.11 and 50% of the b values ranged between 3.04 and 3.24. Somatic growth was isometric for 14 species, hyperallometric for 12 species, while only 5 species grew hypoallometrically. This is the first reference on LWR for sand sole (Pegusa lascaris) in the eastern Mediterranean Sea, while for snake blenny (Ophidion barbatum), common cuttlefish (Sepia officinalis) and deep-water rose shrimp (Parapenaeus longirostris) it is the first LWR in Greek waters.