Spatiotemporal genetic variation of atlantic bluefin tunas from sardinian and mediterranean tuna traps

Tuna traps of the Sardinian and Mediterranean have provided from long to short term series of data and samples of bluefin tuna (BFT) populations inhabiting the Mediterranean. By analyzing genetic variation in BFT trap samples, we have shown that more than one BFT population have been entered and spread in the Mediterranean across the last century and that over short period, the interannual composition of BFT trap catches are genetically constant

Sexual behaviour and reproductive performance of the endangered European eel Anguilla anguilla (Linnaeus, 1758) based on direct observationsand paternity assignment in semi-natural conditions

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

Canning Processes Reduce the DNA-Based Traceability of Commercial Tropical Tunas

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

Quaternary geographical sibling speciation and population structuring in the Eastern Atlantic skates (suborder Rajoidea) Raja clavata and R. straeleni

To access the final version, follow the next link. http://www.springerlink.com/content/t1809472211lk67q/Aim Geographical (allopatric) speciation is a dynamic process whose footprints in the living world are a continuum of stages of increasing divergence. Geographical speciation can also contribute to the evolution of marine taxa. This study looked for two of these evolutionary stages (i.e. structured populations and sibling species) in the diversification patterns of two Atlantic skates (Raja, suborder Rajoidea) which exhibited high morphological and ecological conservativism(undefined

Pokušaji lociranja i uzorkovanja velike bijele psine, Carcharodon carcharias (Lamniformes: Lamnidae), uz talijansku obalu u Sredozemnom moru

Described in the present report are documented attempts to tag and sample the white shark, Carcharodon carcharias (Linnaeus, 1758), along Italian coasts in the Mediterranean Sea, which took place near the Lampedusa Island in the lower Tyrrhenian Channel of Sicily, off the coast of Rimini in the Adriatic Sea, and of Civitavecchia in the central Tyrrhenian Sea. The project, activated in 2015, was aimed at tagging and sampling specimens of the white shark in order to collect data useful to implement conservation strategies in the Mediterranean Sea. Despite four tagging attempts made in 2017, 2018, 2021, and 2022 with 288 total hours of baiting activity and the use of 1030 kg of chum, no white sharks or any other shark species were sighted.U radu su dokumentirani pokušaji označavanja i uzorkovanja velike bijele psine Carcharodon carcharias (Linnaeus, 1758) uz talijansku obalu u Sredozemnom moru. Istraživanje je obavljeno na području oko otoka Lampeduze, u sicilijanskom kanalu u južnom Tirenskom moru, ispred Riminija u Jadranskom moru te kod Civitavecchije u centralnom Tirenskom moru. Projekt, koji je započeo 2015. godine, bio je usmjeren na označavanje i uzorkovanje primjeraka velike bijele psine s ciljem prikupljanja podataka važnih za implementaciju mjera za očuvanje populacije ove vrste u Sredozemnom moru. Unatoč četiri pokušaja označavanja obavljena 2017., 2018., 2021. i 2022. godine, u ukupnom trajanju od 288 sati primamljivanja uz pomoć mamca te 1030 kg mamca, ni jedan primjerak velike bijele psine, ni drugih vrsta morskih pasa, nije primijećen

Isotopic life-history signatures are retained in modern and ancient Atlantic bluefin tuna vertebrae

Isotopic, tagging and diet studies of modern-day teleosts lacked the ability to contextualise life-history and trophic dynamics with a historical perspective, when exploitation rates were lower and climatic conditions differed. Isotopic analysis of vertebrae, the most plentiful hard-part in archaeological and museum collections, can potentially fill this data-gap. Chemical signatures of habitat and diet use during growth are retained by vertebrae during bone formation. Nonetheless, to fulfil their potential to reveal life-history and trophic dynamics, we need a better understanding of the time frame recorded by vertebrae, currently lacking due to a poor understanding of fish bone remodelling. To address this issue, the authors serially-sectioned four vertebral centra of the highly migratory Atlantic bluefin tuna (Thunnus thynnus; BFT) captured off Sardinia (Italy) and analysed their isotopic composition. They show how carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) isotope values can vary significantly across BFT vertebrae growth-axes, revealing patterning in dietary life histories. Further, they find that similar patterns are revealed through incremental isotopic analysis of inner and outer vertebrae centra samples from 13 archaeological BFT vertebrae dating between the 9th and13th centuries CE. The results indicate that multi-year foraging signatures are retained in vertebrae and allow for the study of life histories in both modern and paleo-environments. These novel methods can be extended across teleost taxa owing to their potential to inform management and conservation on how teleost trophic dynamics change over time and what their long-term environmental, ecological and anthropological drivers are

Evaluating genetic traceability methods for captive bred marine fish and their applications in fisheries management and wildlife forensics

Growing demands for marine fish products is leading to increased pressure on already depleted wild populations and a rise in the aquaculture production. Consequently, more captive bred fish are released into the wild through accidental escape or deliberate restocking, stock enhancement and sea ranching programs. The increased mixing of captive bred fish with wild conspecifics may affect the ecological and/or genetic integrity of wild fish populations. From a fisheries management perspective unambiguous identification tools for captive bred fish will be highly valuable to manage risks. Additionally there is great potential to use these tools in wildlife forensics (i.e. tracing back escapees to their origin and determining mislabelling of seafood products). Using SNP data from captive bred and wild populations of Atlantic cod (Gadus morhua L.) and sole (Solea solea L.), we explored the efficiency of population and parentage assignment techniques for the identification and tracing of captive bred fish. Simulated and empirical data were used to correct for stochastic genetic effects. Overall, parentage assignment performed well when a large effective population size characterizes the broodstock and escapees originate from early generations of captive breeding. Consequently, parentage assignments are particularly useful from a fisheries management perspective to monitor the effects of deliberate releases of captive bred fish on wild populations. Population assignment proved to be more efficient after several generations of captive breeding, which makes it a useful method in forensic applications for well-established aquaculture species. We suggest the implementation of a case by case strategy when choosing the best method

Anadara kagoshimensis (Mollusca: Bivalvia: Arcidae) in Adriatic Sea: morphological analysis, molecular taxonomy, spatial distribution, and prediction

Morphological analysis, molecular characterization, and information on distribution and density of Anadara kagoshimensis (Tokunaga, 1906) specimens collected in the Adriatic Sea were here carried out as based on various material and data from five surveys conducted from 2010 to 2014, for a total of 329 bottom trawl hauls. The morphological and molecular analyses allowed to clarify the confused taxonomy regarding the biggest ark clam alien species invading the Italian waters and the Mediterranean Sea. The analysis on distribution and density revealed that A. kagoshimensis mostly occurs along the Italian coast at depths from 8 to 50 m, with a catch frequency of more than 98% in all hauls performed on silty-clay sediment at 8-30 m depth. The hotspot map clearly shows a reduction of its distribution area from 2010 to 2012

Chilomycterus reticulatus (Actinopterygii : Tetraodontiformes : Diodontidae) in the southern Sicilian waters, central Mediterranean Sea

A recently discovered fish specimen representing the family Diodontidae has been documented in the waters off Mazara del Vallo in southwest Sicily, Italy. A detailed description of the morphological and meristic characteristics of the specimen is reported. Molecular identification was performed through sequence analysis of the Cytochrome Oxidase subunit I (COI). The specimen was identified as Chilomycterus reticulatus (Linnaeus, 1758) both morphologically and genetically. The finding marks the third confirmed record of Chilomycterus reticulatus in the Mediterranean Sea and Italian waters. The significance of the presence of this uncommon fish in the basin is briefly discussed, shedding light on its occurrence and potential implications.peer-reviewe

Baseline genetic distinctiveness supports structured populations of thornback ray in the Mediterranean Sea

The thornback ray (Raja clavata) is the most important chondrichthyan in terms of landings in the Mediterranean Sea. Intense harvesting may induce negative genetic effects reducing the resilience of overfished species. For this reason, genetic diversity information should be considered in fisheries management and conservation policies. Microsatellite markers were used to unravel the genetic features (variability, connectivity, sex-biased dispersal) of R. clavata populations, both at the small (around the coast of Sardinia, western Mediterranean Sea) and larger spatial scales (at the pan-Mediterranean level, and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences between Mediterranean and Atlantic rays, as well as within the Mediterranean Sea between its western and eastern basins. The data indicated that both the Strait of Gibraltar and the Sicilian Channel seem to be effective in limiting the dispersal of thornback ray individuals, but a further structuring was identified, with the significant genetic differentiation of the populations located in the Algero-Provençal and Tyrrhenian basins. Such a fine-scale arrangement suggests the occurrence of additional barriers to species dispersal. A lack of significant genetic differentiation, stable over the years, was measured at a local scale among R. clavata Sardinian samples. Several possible mechanisms, both biological and abiotic (e.g. migratory behaviour, waterfronts and oceanographic discontinuities), are discussed. Overall, the genetic data presented, both at the local and regional level, could represent the baseline information for the temporal monitoring of populations and assessing the effects of present or future fisheries-related management actions. The data obtained are information of paramount importance for minimizing the gaps in our current knowledge of the genetic diversity of thornback rays and maximizing the information needed for the correct protection of R. clavata populations