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Climate change and size-selective overexploitation can alter fish size and growth, yet our understanding of how and to what extent is limited due to a lack of long-term biological data from wild populations. This precludes our ability to effectively forecast population dynamics and support sustainable fisheries management. Using modern, archived, and archaeological vertebrae dimensions and growth rings of one of the most intensely exploited populations, the eastern Atlantic and Mediterranean bluefin tuna (Thunnus thynnus, BFT), we estimated catch-at-size and early-life growth patterns from the 3rd century bce to the 21st century ce to understand responses to changes in its environment. We provide novel evidence that BFT juvenile growth increased between the 16th–18th, 20th, and 21st centuries, and is correlated with a warming climate and likely a decrease in stock biomass. We found it equally plausible that fisheries-induced evolution has acted to increase juvenile BFT growth, driving earlier maturation as a result of size-selective exploitation. Coincidently, we found limited evidence to suggest a long history of large ( >200 cm FL) BFT capture. Instead, we found that the catch-at-size of archaeological BFT was relatively small in comparison with more intensive, 20th and 21st century tuna trap fisheries which operated further from shore. This complex issue would benefit from studies using fine-scale biochronological analyses of otoliths and adaptation genomics, throughout the last century especially, to determine evolutionary responses to exploitation, and further disentangle the influence of temperature and biomass on fish growth.

Despite a high species diversity, skates (Rajiformes) exhibit remarkably conservative morphology and ecology. Limited trait variations occur within and between species, and cryptic species have been reported among sister and non-sister taxa, suggesting that species complexes may be subject to stabilising selection. Three sibling species are currently recognised in the Raja miraletus complex: (i) R. miraletus occurring along the Portuguese and Mediterranean coasts, (ii) R. parva in the Central-Eastern Atlantic off West Africa and (iii) R. ocellifera in the Western Indian Ocean off South Africa. In the present study, the genetic variation at mitochondrial and nuclear markers was estimated in the species complex by analysing 323 individuals sampled across most of its geographical distribution area to test the hypothesis that restricted gene flow and genetic divergence within species reflect known climate and bio-oceanographic discontinuities. Our results support previous morphological studies and confirm the known taxonomic boundaries of the three recognised species. In addition, we identified multiple weakly differentiated clades in the Northeastern Atlantic Ocean and Mediterranean, at least two additional cryptic taxa off Senegal and Angola, a pronounced differentiation of ancient South African clades. The hidden genetic structure presented here may represent a valuable support to species’ conservation action plans.

1. The Mediterranean starry ray (Raja asterias) populations within the Mediterranean Sea are susceptible to high rates of bycatch in the multispecies trawl fisheries. Understanding its population structure and identifying critical habitats are crucial for assessing species vulnerability and setting the groundwork for specific management measures to prevent population decline. 2. To assess the population structure of R. asterias in the Mediterranean, the genetic variation in nine population samples at one mitochondrial marker and eight nuclear microsatellite loci was analysed. Moreover, 172 egg cases collected in the Strait of Sicily were identified at species level using integrated molecular and morphological approaches. 3. Genetic analyses revealed that the Mediterranean starry ray comprises three distinct units inhabiting the western, the central-western, and the central-eastern areas of the Mediterranean. An admixture zone occurs in the Strait of Sicily and the Ionian Sea, where individuals of the central-western and central-eastern population units intermingle. 4. The joint morphometric–genetic analyses of rajid egg cases confirmed the presence of more than one species in the admixture area, with a predominance of egg cases laid by R. asterias. DNA barcoding revealed that egg cases and embryos of R. asterias shared several haplotypes with adult individuals from the centralwestern and central-eastern Mediterranean Sea, revealing that females of both populations laid numerous eggs in this area. 5. According to these findings, detailed taxonomic determination of egg cases, when combined with seasonal migration studies, could improve the capability to identify important spawning or nursery areas for the Mediterranean starry ray, particularly in those admixture zones relevant to maintaining genetic diversity. 6. Finally, these new insights should be considered to update the Action Plan for the Conservation of Cartilaginous Fishes in the Mediterranean Sea with effective measures to reduce the impact of skate bycatch in trawling and safeguard egg cases in nursery areas.

9 pages, 3 figures, 1 table.-- Open Access, Atlantic bluefin tuna (Thunnus thynnus; BFT) is a large (up to 3.3 m in length) pelagic predator which has been exploited throughout the eastern Atlantic and Mediterranean since prehistoric times, as attested by its archeological remains. One key insight derivable from these remains is body size, which can indicate past fishing abilities, the impact of fishing, and past migration behavior. Despite this, there exists no reliable method to estimate the size of BFT found in archeological sites. Here, 13 modern Thunnus spp. skeletons were studied to provide power regression equations that estimate body length from vertebra dimensions. In modern specimens, the majority of BFT vertebrae can be differentiated by their morphological features, and thus, individual regression equations can be applied for each rank (position in vertebral column). In an archeological context, poor preservation may limit one's ability to identify rank; hence, “types” of vertebrae were defined, which enable length estimates when rank cannot be determined. At least one vertebra dimension, height, width, or length correlated highly with body length when vertebrae were ranked (R2 > 0.97) or identified to types (R2 > 0.98). Whether using rank or type, length estimates appear accurate to approximately ±10%. Finally, the method was applied to a sample of Roman-era BFT vertebrae to demonstrate its potential. It is acknowledged that further studies with larger sample sizes would provide more precision in BFT length estimates, This work is a contribution to the MSCA SeaChanges ITN and was funded by EU Horizon 2020 (H2020 Marie Skłodowska-Curie Actions, Grant Number: 813383). Open Access Funding provided by Universita degli Studi di Bologna within the CRUI-CARE Agreement

14 pages, 4 figures, 3 tables, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2022.953895/full#supplementary-material.-- Data availability statement: The data presented in this study are included in the supplementary material (SM1; SM10), further inquiries can be directed to the corresponding authors, Among the main measures adopted to reduce anthropogenic impacts on elasmobranch communities, understanding the ecology of deep-sea sharks is of paramount importance, especially for potentially vulnerable species highly represented in the bycatch composition of commercial fisheries such as the blackmouth catshark Galeus melastomus. In the present work, we unravelled the first indication of population genetic structure of G. melastomus by using a novel and effective panel of nuclear, and polymorphic DNA markers and compared our results with previous findings supporting high genetic connectivity at large spatial scales. Given the lack of species-specific nuclear markers, a total of 129 microsatellite loci (Simple Sequence Repeats, SSRs) were cross-amplified on blackmouth catshark specimens collected in eight geographically distant areas in the Mediterranean Sea and North-eastern Atlantic Ocean. A total of 13 SSRs were finally selected for genotyping, based on which the species exhibited signs of weak, but tangible genetic structure. The clearcut evidence of genetic differentiation of G. melastomus from Scottish waters from the rest of the population samples was defined, indicating that the species is genetically structured in the Mediterranean Sea and adjacent North-eastern Atlantic. Both individual and frequency-based analyses identified a genetic unit formed by the individuals collected in the Tyrrhenian Sea and the Strait of Sicily, distinguished from the rest of the Mediterranean and Portuguese samples. In addition, Bayesian analyses resolved a certain degree of separation of the easternmost Aegean sample and the admixed nature of the other Mediterranean and the Portuguese samples. Here, our results supported the hypothesis that the interaction between the ecology and biology of the species and abiotic drivers such as water circulations, temperature and bathymetry may affect the dispersion of G. melastomus, adding new information to the current knowledge of the connectivity of this deep-water species and providing powerful tools for estimating its response to anthropogenic impacts, This research was funded by RFO and Canziani grants given to FT and AC, and by the RFO grant of the University of Bologna for the research fellowships of AF, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Aim: Determine the evolutionary origin of the heretofore poorly characterized contemporary Great White Shark (GWS; Carcharodon carcharias) of the Mediterranean Sea, using phylogenetic and dispersal vicariance analyses to trace back its global palaeo-migration pattern. Location: Mediterranean Sea. Taxon: Carcharodon carcharias. Methods: We have built the largest mitochondrial DNA control region (CR) sequence dataset for the Mediterranean GWS from referenced historical jaws spanning the 19th and 20th centuries. Mediterranean and global GWS CR sequences were analysed for genetic diversity, phylogenetic relationships and divergence time. A Bayes factor approach was used to assess two scenarios of GWS lineage divergence and emergence of the Mediterranean GWS line using fossil records and palaeo-geographical events for calibration of the molecular clock. Results: The results confirmed a closer evolutionary relationship between Mediterranean GWS and populations from Australia–New Zealand and the North-eastern Pacific coast rather than populations from South African and North-western Atlantic. The Mediterranean GWS lineage showed the lowest genetic diversity at the global level, indicating its recent evolutionary origin. An evaluation of various divergence scenarios determined the Mediterranean GWS lineage most likely appeared some 3.23 million years ago by way dispersal/vicariance from Australian/Pacific palaeo-populations. Main conclusion: Based on the fossil records, phylogeographic patterns and divergence time, we revealed that the Mediterranean GWS population originated in the Pliocene following the Messinian Salinity Crisis. Colonization of the Mediterranean by GWS likely occurred via an eastward palaeo-migration of Australian/eastern Pacific elements through the Central American Seaway, before the complete closure of the Isthmus of Panama. This Pliocene origin scenario contrasts with a previously proposed scenario in which Australian GWS colonized the Mediterranean via antipodean northward migration resulting from navigational errors from South Africa during Quaternary climatic oscillations.

The actual occurrence of Squalus megalops in the Mediterranean Sea has recently been questioned. Several research works which sought to assess available morphological and meristic features that differentiate S. megalops from other Squalus species in the Mediterranean Sea, revealed poor discriminatory power and high variability of the assessed characters, especially when comparing S. megalops and S. blainville. The application of molecular tools does not support the presence of S. megalops. In the present study, we screened spurdog species from the Strait of Sicily using a molecular taxonomy approach based on two mitochondrial DNA markers and we report the occurrence of two Squalus lineages characterizing specimens collected from the stretch of sea between Tunisia, southern Sicily, Malta and Libya. The results support the hypothesis that a common species, S. blainville, currently inhabits the Mediterranean Sea, while a second and rare species is probably an occasional visitor with high morphological similarity to the S. megalops and S. blainville but is genetically distinct from both. Within this perspective, the occurrence of S. megalops in the Mediterranean Sea is not confirmed and our study highlights the taxonomic uncertainties in relation to the occurrence and distribution of Squalus species in this region. We encourage the establishment of a coordinated international effort to implement a comprehensive and integrated taxonomic assessment on this genus which represents an irreplaceable component of the biodiversity of the area.

26 pages, 8 figures, 2 tables, supporting information https://doi.org/10.1093/zoolinnean/zlab110.-- Data availability: Sequences and data on specimens are available on GenBank and Bold databases, as specified in the main text, The current shift of fishery efforts towards the deep sea is raising concern about the vulnerability of deep-water sharks, which are often poorly studied and characterized by problematic taxonomy. For instance, in the Mediterranean Sea the taxonomy of genus Centrophorus has not been clearly unravelled yet. Since proper identification of the species is fundamental for their correct assessment and management, this study aims at clarifying the taxonomy of this genus in the Mediterranean Basin through an integrated taxonomic approach. We analysed a total of 281 gulper sharks (Centrophorus spp.) collected from various Mediterranean, Atlantic and Indian Ocean waters. Molecular data obtained from cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S), NADH dehydrogenase subunit 2 (ND2) and a portion of a nuclear 28S ribosomal DNA gene region (28S) have highlighted the presence of a unique mitochondrial clade in the Mediterranean Sea. The morphometric results confirmed these findings, supporting the presence of a unique and distinct morphological group comprising all Mediterranean individuals. The data strongly indicate the occurrence of a single Centrophorus species in the Mediterranean, ascribable to C. cf. uyato, and suggest the need for a revision of the systematics of the genus in the area, This research was partially funded by the University of Bologna through ‘RFO’ and ‘Canziani’ grants given to FT and AC and by the European Commission Directorate – General Fisheries in the framework of the MEDITS survey. RM and LC acknowledge the support for their research grants to funds granted by the Università degli Studi di Cagliari ‘UNICA-RICCAR_2013_CAU_02’ and Ministero dell’Università e della Ricerca ‘PON AIM 1854833 - PON Ricerca e Innovazione 2014-2020 – Azione I.2 - D.D. n. 407, 27/02/2018 – Attraction and International Mobility’, respectivel, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Overexploitation has directly, negatively affected marine fish populations in the past half-century, modifying not only their abundance but their behaviour and life-history traits. The recovery and resilience of such populations is dependent upon their exploitation history, which often extends back millennia. Hence, data on when exploitation intensified and how populations were composed in historical periods, have the potential to reveal long-term population dynamics and provide context on the baselines currently used in fisheries management and conservation. Here, we setup a framework for investigations on the exploitation history of Atlantic bluefin tuna (Thunnus thynnus; BFT) in the eastern Atlantic and Mediterranean by collating records of their zooarchaeological remains and critically reviewing these alongside the literature. Then, we outline how novel multidisciplinary applications on BFT remains may be used to document long-term population dynamics. Our review of literature provides clear evidence of BFT overexploitation during the mid-20th century ce. Furthermore, a strong case could be made that the intensification of BFT exploitation extends back further to at least the 19th century ce, if not the 13th–16th century ce, in the eastern Atlantic and Mediterranean. However, a host of archaeological evidence would suggest that BFT exploitation may have been intensive since antiquity. Altogether, this indicates that by the currently used management baselines of the 1970s, population abundance and complexity was already likely to have declined from historical levels, and we identify how biomolecular and morphometric analyses of BFT remains have the potential to further investigate this.

The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated with shared fisheries management. In an effort to resolve the species' stock dynamics, a genomewide search for spatially informative single nucleotide polymorphisms (SNPs) was undertaken, by way of sequencing reduced representation libraries. An allele frequency approach to SNP discovery was used, combining the data of 555 larvae and young-of-the-year (LYOY) into pools representing major geographical areas and mapping against a newly assembled genomic reference. From a set of 184,895 candidate loci, 384 were selected for validation using 167 LYOY. A highly discriminatory genotyping panel of 95 SNPs was ultimately developed by selecting loci with the most pronounced differences between western Atlantic and Mediterranean Sea LYOY. The panel was evaluated by genotyping a different set of LYOY (n = 326), and from these, 77.8% and 82.1% were correctly assigned to western Atlantic and Mediterranean Sea origins, respectively. The panel revealed temporally persistent differentiation among LYOY from the western Atlantic and Mediterranean Sea (FST = 0.008, p = .034). The composition of six mixed feeding aggregations in the Atlantic Ocean and Mediterranean Sea was characterized using genotypes from medium (n = 184) and large (n = 48) adults, applying population assignment and mixture analyses. The results provide evidence of persistent population structuring across broad geographic areas and extensive mixing in the Atlantic Ocean, particularly in the mid-Atlantic Bight and Gulf of St. Lawrence. The genomic reference and genotyping tools presented here constitute novel resources useful for future research and conservation efforts., This work was carried out under the provision of the ICCAT Atlantic-wide Research Programme for Bluefin Tuna (GBYP), funded by the European Union, by several ICCAT CPCs, the ICCAT Secretariat and other entities (see: http://www.iccat.int/GBYP/en/Budget.htm). Additional funds were provided by the MARES Joint Doctorate Programme Selected Under Erasmus Mundus and coordinated by Ghent University (FPA 2011-0016). Larvae from the Balearic Sea were provided by the ATAME project “Bluefin tuna abundance indices: towards recruitment estimators based on larval ecology” (CTM 2011-29525-C04-02) and the BLUEFIN project “Modelling bluefin spawning areas variability and population dynamics in the Western Mediterranean” (IEO-SOCIB agreement).

The seahorse Hippocampus guttulatus reaches its highest abundance in confined environments, where it has unique biological and ecological traits that suggest significant genetic differentiation among populations. In the present study, we aimed to reveal the genetic structure of this species by analysing eight microsatellite loci and a mitochondrial DNA region (cytochrome b) of eight populations from the Central–Western Mediterranean Sea, including lagoon sites. Levels of genetic diversity, as measured by the total number of alleles, number of private alleles, allelic richness and heterozygosity, ranged from low to moderate. The overall value of inbreeding was high, indicating a deficiency in heterozygotes. The haplotype network had a star-like construction, with the most common haplotype present in all populations. Data from the two molecular markers congruently displayed a similar pattern and revealed low genetic differentiation, notwithstanding predictions based on species traits. The observed genetic structure is probably the result of both historical population demographic events and current gene flow. The investigated lagoons, however, revealed a unique genetic profile, which is especially highlighted by the Taranto population. At this site, the results also showed altered values of observed/expected heterozygosity and allelic richness, a characteristic of marginal populations. Our study suggests that lagoon populations should be managed as distinct genetic units.

European eel Anguilla anguilla is among the highly valued species for aquaculture. Since its peculiar biology, it is not yet possible to complete the whole life cycle in artificial conditions and its supply depends entirely on wild catches. In the last 50 years this species has suffered a population reduction of 99 % mainly due to overfishing. In a conservation perspective, it is of fundamental importance to improve the aquaculture production of European eel, to avoid the extinction of this species and preserve its residual genetic variability, allowing at the same time the fulfilling of costumers request without increasing its harvesting pressure.In this study we aimed to deepen the knowledge about the mechanisms at the basis of reproduction of the European eel in semi-natural conditions, through direct observation of spawning behaviour and through the paternity assignment using microsatellite markers. The systematic and prolonged observation of the reproductive behaviour of European eel and the contextual parentage analyses we carried out for the very first time in this species on 39 adults and 432 F1 randomly collected. We contributed to unravel the sexual behaviour of this species in the most common artificial reproduction conditions (polyandry), and define the precise courtship sequence until the release of gametes, and the male-male hierarchy in courtship. We characterized for the first time three main types of male: dominant (the first who starts the courtship, and the one with the majority of F1 assigned), subordinate (which starts the courtship only in a second time and with a minor percentage of F1 ascribed) and ineffective (which sometime appears totally disinterested to courtship and has few F1 or none).The evidences here produced represent an important attempt for developing good reproduction practices of the critically endangered European eel, providing a good starting point for its future aquaculture production. Keywords: Anguilla anguilla, Aquaculture, Artificial breeding, Kinship analysis, Parentage assignment

International audience; Skates are characterised by conservative body morphology which hampers identification and leads to frequent taxonomic confusion and market mislabelling. Accurate specimen classification is crucial for reliable stock assessments and effective conservation plans, otherwise the risk of extinction could be unnoticed. The misclassification issue is evident for the genus Dipturus, distributed worldwide, from the continental shelf and slope to the deep sea. In this study, barcode cytochrome oxidase I gene (COI) sequences were used along with species delimitation and specimen assignment methods to improve taxonomy and zoogeography of species of conservation interest inhabiting the Atlantic Ocean and Mediterranean Sea. In this study, we provided new evidence of the occurence of D. nidarosiensis in the Central-Western Mediterranean Sea and the lack of Atlantic-Mediterranean genetic divergence. The Atlantic endangered species D. laevis and D. batis clustered together under the same molecular operational taxonomic unit (MOTU) with any delimitation methods used, while the assignment approach correctly discriminated specimens into the two species. These results provided evidence that the presence of the barcode gap is not an essential predictor of identification success, but the use of different approaches is crucially needed for specimen classification, especially when threshold-or tree-based methods result less powerful. The analyses also showed how different putative, vulnerable, species dwelling across SouthWestern Atlantic and SouthEastern Pacific are frequently misidentified in public sequence repositories. Our study emphasised the limits associated to public databases, highlighting the urgency to verify and implement the information deposited therein in order to guarantee accurate species identification and thus effective conservation measures for deep-sea skates.

Conservation and long-term management plans of marine species need to be conceived upon a universally recognised key-feature: species identity. This important assignment resulted particularly arduous among skates (order Rajiformes), in which the phenotypic similarity between some taxa and the individual variability in others, entangled accurate species identification. This study confirms the power of DNA barcoding for the discrimination between skate species across the Atlantic Ocean and for its use as effective tool to minimize the risk of species misidentification and to elucidate species boundaries. In this perspective, this work compiles and establish a new fully available and well-curated barcode library, the ELASMO-ATL project, which gathered biological and molecular information of 432 skate specimens and covered coastal waters of four FAO Major Fishing Areas (27, 34, 47, 41) of the Atlantic Ocean. The evolutionary histories of 34 skate species were estimated with two concatenated mitochondrial markers (COI and NADH2) through Bayesian and species level phylogeny analyses. It was possible to discover a new evolutionary lineage within the genus Raja in the southern-most part of its distribution area and to enable deepening the relationship between South-African endemic species of Rajella. Once again, Western South African coasts and oceanographic fronts may play a fundamental role among skates’ speciation events in which the paleoclimatic and paleogeographic history joined to hydrography events could have contributed to the formation of refugial areas, characterised by geographical isolation. Subsequent contact zones in these areas between Senegal and Angola seems to constitute a continuum/cline of genetic change among some Raja species. These data successfully resolved many taxonomic ambiguities and demonstrated a highly cohesive monophyletic clustering among the order laying the foundations for further inference of evolutionary patterns suitable for addressing management and conservation issue.

The worldwide abundance of Galeus melastomus in the biological composition of fishery bycatch led to consider this species as a key-taxon for understanding the mysterious biology and ecology of sharks living in deep ecosystems. With the present work, we aim to unravel the population structure of the blackmouth catshark in the Mediterranean Sea and adjacent North-Eastern Atlantic with the use of nuclear molecular markers (simple sequence repeats, SSRs) and compare our results with recent findings based on mitochondrial DNA supporting total panmixia in the species. Given the absence of species-specific microsatellite markers we attempted the cross-amplification of a panel of 129 SSRs developed for Centroselachus crepidater, Galeorhinus galeus, Hexanchus griseus, Mustelus antarcticus, M. canis, M. henlei, M. mustelus, Negaprion brevirostris, Scyliorhinus canicula, Squalus acanthias and S. mitsukurii on blackmouth catsharks collected during scientific surveys undertaken in different years. The rationale of the chosen methodology was based on the calculation of genetic distances between NADH2 sequences (1044bp long) derived from 595 species of elasmobranchs. Our strategy focused on testing first SSRs markers developed on closely-related species. Then, we assessed highly polymorphic markers developed on non-closely-related species. After a pilot gradient amplification on few individuals from three different geographic macro-areas, we screened a total of 24 samples at the established conditions. To date, 16 microsatellite loci have been classified as potential candidates for the succesful cross-amplification on Atlantic and Mediterranean samples of G. melastomus. These candidate loci will be applied in the population genetic analysis delineated in the Atlantic Ocean (two sites) and in the Mediterranean Sea (five sites). Hopefully, the higher resolution power of the markers chosen for this study will be able to disclose any signal of genetic structure of the blackmouth catsharks and will contribute to improve the knowledge on deep-sharks.

Among skates, Rajidae represents one of the most enigmatic family of cartilaginous fish whose bio- ecological traits contributed to an extraordinary evolutionary success in terms of species richness and endemism. Past and present taxonomic conflicts and species misidentifications are linked to their extraordinary level of morphological stasis. In recent years, these issues have been overcome by wide- scale molecular taxonomy analyses, but also raised questions about their evolutionary history. Concerted actions as the ELASMOMED and ELASMOATL initiatives encouraged and improved large-scale sampling efforts in the Mediterranean and Eastern Atlantic Ocean over years, building unique voucher repositories of thousands of specimens and enabling the exploration of skates’ biogeography. Here, the maximum taxonomic (51 OTUs) and molecular (47 OTUs) diversity of tribes Rajini and Amblyrajini were measured using concatenated mitochondrial genes. We also estimated their evolutionary divergence using the molecular clock approach. Evidences produced so far showed that, despite the ancient origin of Rajidae (97 MYA), the Eastern Atlantic and Mediterranean faunas originated more recently, after the closure of connection between these areas and the Indo-Pacific Ocean (15 MYA). The endemic Mediterranean species originated with the recolonization of the Basin, after the Messinian salinity crisis (7-5 MYA). At least five independent vicariant events contributed from 7.4 to 3.15 MYA to the formation of allopatric or parapatric sister species, each distributed in the N-E Atlantic and S-E Atlantic respectively. On the whole, the Quaternary tectonic movement of continental masses, paleoclimatic events and present oceanographic discontinuities occurring along the western African continental shelf might explain this series of parallel and independent speciation events related to the maintenance of low or null levels of gene flow between closely related sibling and cryptic species.

Background: A growing concern in conserving threatened animals affected by human impact has been significant worldwide. Among marine animals, sawfishes (Chondrichthyes, Pristidae) are considered one of the most endangered families among lasmobranchs, resulting in extinction in many coastal areas around the world, including the Mediterranean Sea. Here, sawfish ccurred with two species, Pristis pristis and P. pectinata, until the second half of the last century and are now considered Critically ndangered/Possibly Extinct. The historical occurrence of sawfish in the area is documented by bibliographic/ archival records and y numerous preserved historical rostra available in museum collections. In this study we attempted to genetically characterize the istorical remains of sawfish from several European museums and to enable the investigation of their evolutionary and ecological relationships with global samples. Results: A total of 80 rostra specimens, dated from 1700 to 1900 and catalogued as unknown origin or Mediterranean (11), were collected from 11 European museums and were properly prepared for ancient DNA genetic analysis. Taxonomic identification at the species level was obtained through PCR amplification of small fragments (150 bp) of two mitochondrial markers commonly used for species identification (i.e., the mitochondrial COII and the NADH 2). Sequence comparison with currently available ones from public repositories and phylogenetic tree analyses indicated that the historical specimens belonged to four species, P. pristis, P. zijsron, P. pectinata, and Anoxypristis cuspidate, with a high frequency of mismatches (69%) between molecular identification and species museum cataloguing, when present. These preliminary data also showed the presence of two sequence sub-clusters in the poorly barcoded species P. zijsron. Significance: With the expansion of this initial analysis, we will contribute to increase the limited olecular data of these critically endangered large predators and to exploit historical genetic data for reconstructing phylogenetic/phylogeographic extent of the possibly extinct population of Mediterranean sawfish.

Canned tuna is one of the most widely traded seafood products internationally and is of growing demand. There is an increasing concern over the vulnerability of canned tuna supply chains to species mislabelling and fraud. Extensive processing conditions in canning operations can lead to the degradation and fragmentation of DNA, complicating product traceability. We here employed a forensically validated DNA barcoding tool (cytochrome b partial sequences) to assess the effects of canning processes on DNA degradation and the identification of four tropical tuna species (yellowfin, bigeye, skipjack and longtail tuna) collected on a global scale, along their commercial chains. Each species was studied under five different canning processes i.e., freezing, defrosting, cooking, and canning in oil and brine, in order to investigate how these affect DNA-based species identification and traceability. The highest percentage of nucleotide substitutions were observed after brine-canning operations and were greatest for yellowfin and skipjack tuna. Overall, we found that DNA degradation significantly increased along the tuna canning process for most specimens. Consequently, most of the specimens canned in oil or brine were misidentified due to the high rate of nucleotide substitution in diagnostic sequences.

How the size of female yellowfin tuna (Thunnus albacares) affects their spawning capability and fecundity is still an open and unresolved question due to the difficulties in investigating these complex effects in highly migratory pelagic marine fish species. However, this information is key to understanding the reproductive potential and resilience of the stock. We investigate how energetic resources are allocated for reproduction by female yellowfin tuna according to their size in the Gulf of Guinea (central-eastern Atlantic Ocean). Our results reveal that larger females have not only larger ovaries by virtue of their greater abdominal cavity, but also different fatty acid profiles in the gonads compared to smaller females, with potential effects on their spawning and recruitment patterns. This study contributes to the knowledge of size-dependent variation in female yellowfin tuna and paves the way for future studies on size-dependent effects on reproductive parameters in this species.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Anguilla anguilla (Linnaeus, 1758) is a critically endangered species, whose existence in the wild is highly threatened by human activities and is included in the IUCN Red List of threatened species as “Critically Endangered”. Restocking and captive breeding programs designed to preserve the residual genetic variability should represent the future for conservation of this species. In this perspective, the present study aims to increase the knowledge about the mechanisms at the basis of reproduction of the European eel in semi-natural conditions, through paternity assignment. Here we show the very first parental assignment results of a plenty successful reproductive event that occurred in 2016: four families of European eel founded by four female plus 11 males in different mixes and their progeny, for a total of 206 samples. Parental allocations revealed the presence of different percentage of success of males in fertilizing eggs, with two “super-males” at the top of the productivity, with the 19.9% and 18.8% of total larvae (males 128 and 129) and two “weak-males” at the end of the distribution of productivity curve (males 134 and 135). Since the artificial reproduction of European eel is a very challenging topic for world aquaculture, these first results may help in drawing future breeding plans aimed both to increase the productivity for human consumption and to develop restocking plans in order to try to reduce the speed of decreasing in worldwide stocks of European eels.

Local adaptation is often found to be in a delicate balance with gene flow in marine species with high dispersal potential. Genotyping with mapped transcriptome-derived markers and advanced seascape statistical analyses are proven tools to uncover the genomic basis of biologically relevant traits under environmental selection. Using a panel of 426 gene-linked single nucleotide polymorphisms (SNPs), we scanned 17 samples (n¼539) of sole (Solea solea L.) from the Northeast Atlantic Ocean and applied a node-based seascape analysis. Neutral loci confirmed a clear distinction between the North Sea–Baltic Sea transition zone and the other Eastern Atlantic samples. At a more subtle level, the latter unit split in an English Channel and North Sea group, and a Bay of Biscay and Atlantic Iberian coast group. A fourth group, the Irish and Celtic Sea, was identified with 19 outlier loci. A pattern of isolation by distance (IBD) characterized the latitudinal distribution. Seascape analyses identified winter seawater temperature, food availability and coastal currents to explain a significant component of geographically distributed genetic variation, suggesting that these factors act as drivers of local adaptation. The evidence for local adaptation is in line with the current understanding on the impact of two key ecological factors, the life-history trait winter mortality and the behaviour of inshore/offshore spawning. We conclude that the subtle differentiation between two metapopulations (North Sea and Bay of Biscay) mirrors local adaptation. At least three genomic regions with strong population differentiation point to locally divergent selection. Further functional characterization of these genomic regions should help with formulating adaptive management policies.