Preliminary study on otolith chemistry and otolith morphology of two demersal fish species, European hake Merluccius merluccius (Linnaeus, 1758) and striped red mullet (Mullus surmuletus, Linnaeus, 1758) in the Sea of Marmara

Otoliths are calcium carbonate (CaCO3) accumulations. Under the influence of different ecosystems morphological and chemical composition change. In this study, economically important two demersal fish species; European hake Merluccius merluccius (Linnaeus, 1758) and Stripet red mullet (Mullus surmuletus Linnaeus, 1758) was examined. Otoliths (Sagitta) belonging to these two species have been studied both chemically and morphologicall. Morphometric measurements of otoliths (length, mm; width, mm; area, mm2; perimeter, mm) in the sagittal of each species was made by the Leica M125 tri-ocular microscope. In the chemical analysis of otoliths, strontium (Sr), magnesium (Mg) and calcium (Ca) trace element amounts, the ratios of Sr and Mg trace elements to Ca element (Sr/Ca and Mg/Ca) were determined. For the micro-chemical analysis of otoliths ICP-MS was used. The highest magnesium (24.92±9.57 mmol/mol) and strontium (26.17±1.81 mmol/mol) element values were found in the otolith of red mullet. The difference between strontium (Sr) and magnesium (Mg) amounts for two fish species was found to be significant (P<0.05). In addition to it was found that the difference between them in the amount of calcium is significant (P<0.001). The shape indexes of otoliths are significantly different between the two fish species. Especially in terms of roundness (RD) and aspect ratio (AR) (P<0.001). The results of this study provide information about the habitats of two economic importance demersal fish species. Since such studies can give information about the habitat areas of fish species, they are important for tracking stocks, migration routes and sustainable fisheries.

Radiological risks assessment due to natural radioactivity in Mediterranean sea fishes

Background and Objectives: In this article a comprehensive study was carried out for the determination of natural radioactivity in Mediterranean sea fishes and the evaluation of radiological health risks due to their ingestion. All analyzed samples came from the Calabria region, southern Italy, and, in particular, from the district of Reggio Calabria. Method: A total of seventy representative samples, five for each investigated species (Sardina Pilchardus, Mugil Cephalus, Scomber Scombrus, Sparus Aurata, Dicentrarchus Labrax, Tonnus Thynnus, Thunnus Alalunga, Xiphaias Gladius, Pagellus Erythrinnus, Engraulis Encrasicholus, Belone Belone, Solea Solea, Merluccius Merluccius, Mullus Surmuletus) were analyzed through HPGe gamma spectrometry. The evaluation of dose levels and lifetime cancer risks for adult members of the population due to the fishes ingestion was also performed. Results: The specific activity of 40K was investigated and its mean value was found to be: (157 ± 17) for Sardina Pilchardus, (138 ± 14) for Mugil Cephalus, (118 ± 13) for Scomber Scombrus, (128 ± 14) for Sparus Aurata, (146 ± 17) for Dicentrarchus Labrax, (93 ± 11) for Tonnus Thynnus, (137 ± 15) for Thunnus Alalunga, (98 ± 10) for Xiphaias Gladius, (105 ± 12) for Pagellus Erythrinnus, (132 ± 14) for Engraulis Encrasicholus, (113 ± 12) for Belone Belone, (34 ± 5) for Solea Solea, (76 ± 9) for Merluccius Merluccius and (96 ± 11) for Mullus Surmuletus, respectively. Conclusions: The committed effective dose and the lifetime cancer risks for adult members of the population due to the consumption of the investigated samples are lower than the average world value, the maximum acceptable level and the allowed range, respectively. It can then be concluded that the Mediterranean sea fishes consumed in the study area pose no significant health risks to the population from a radiological point of view.

Αλιευτική δραστηριότητα και στρατηγικές διαχείρισης της μικρής παράκτιας αλιείας στα Δωδεκάνησα

Παραδοσιακά, η μικρή παράκτια αλιεία συσχετίζεται σε μεγάλο βαθμό με τους κοινωνικοοικονομικούς παράγοντες των παράκτιων και νησιωτικών περιοχών της Μεσογείου. Υπάρχει μεγάλο ενδιαφέρον για την εξασφάλιση της βιώσιμης εκμετάλλευσης και βιωσιμότητάς της. Η παρούσα έρευνα περιγράφει την μικρή παράκτια αλιεία στα Δωδεκάνησα (Κάλυμνος, Κως, Λέρος, Πάτμος, Σύμη), που φιλοξενεί τον μεγαλύτερο παράκτιο στόλο στην ανατολική Μεσόγειο. Επιπλέον, αυτή η έρευνα στοχεύει στην αξιολόγηση της οικονομικής βιωσιμότητας του αλιευτικού στόλου της μικρής παράκτιας αλιείας, με βάση τον υπολογισμό οικονομικών δεδομένων. Μια πολυπαραγοντική ανάλυση χρησιμοποιήθηκε για τον προσδιορισμό των ενασχολήσεων, εισάγοντας τους κύριους πόρους και τα δεδομένα αλιευτικών εργαλείων, που καταγράφηκαν κατά την εκφόρτωση. Οι πιο σημαντικές ενασχολήσεις που αφορούσαν τα αλιευτικά εργαλεία και τα είδη-στόχους είναι: απλάδια δίχτυα, Boops boops, μανωμένα δίχτυα, Scorpaena porcus and Mullus surmuletus, στάσιμα παραγάδια, Pagellus erythrinus, Pagrus pagrus, Diplodus sargus, παρασυρόμενα παραγάδια, Xiphias gladius και μπραγκαρόλα, Octopus vulgaris. Η οικονομική ανάλυση πραγματοποιήθηκε με στόχο την παρουσίαση μιας μεθοδολογίας για την αναγνώριση της σημασίας του αλιευτικού στόλου της μικρής παράκτιας αλιείας, βάσει οικονομικών δεδομένων και τεχνικών χαρακτηριστικών του αλιευτικού στόλου. Το νησί της Καλύμνου αξίζει ιδιαίτερη προσοχή καθώς φιλοξενεί τον μεγαλύτερο και πιο ενεργό παράκτιο αλιευτικό στόλο. Η παρούσα έρευνα αναλύει την αλιεία με παραγάδια και δίχτυα, όπου αυτή δραστηριοποιείται στο νησί της Καλύμνου. Για την αναγνώριση των ενασχολήσεων χρησιμοποιήθηκε πολυπαραγοντική ανάλυση. Οι οικονομικοί δείκτες στο νησί της Καλύμνου υπολογίστηκαν για τις ενασχολήσεις όπου ταυτοποιήθηκαν. Έξι κύριες ενασχολήσεις αναγνωρίστηκαν με τη χρήση των αλιευτικών εργαλείων: στάσιμα παραγάδια, παρασυρόμενα παραγάδια, μπραγκαρόλα και καλαμαριέρα και στόχευαν στα είδη P. pagrus, Diplodus vulgaris, P. erythrinus, Sparus aurata, X. gladius, O. vulgaris και Loligo vulgaris. Όλες οι ενασχολήσεις παρουσίασαν θετική ακαθάριστη ταμειακή ροή, ειδικά όταν στόχευαν στα είδη X. gladius, P. pagrus, D. vulgaris, P. erythrinus και S. aurata. Τέσσερεις κύριες ενασχολήσεις παρατηρήθηκαν με τη χρήση των αλιευτικών εργαλείων απλάδια και μανωμένα δίχτυα, με είδη στόχου Mullus barbatus, B. boops, M. surmuletus, S. porcus και Sepia officinalis. Οι δυο από τις τέσσερεις κύριες ενασχολήσεις, όπου στόχευαν στα είδη B. boops S. porcus και S. officinalis ήταν οικονομικά αποδοτικότερες. Τα αποτελέσματα παρείχαν ουσιαστικές πληροφορίες για την ανάπτυξη και την εφαρμογή σχεδίων διαχείρισης που αφορουν τη βιωσιμότητα της μικρής παράκτιας αλιείας.

Polycyclic aromatic hydrocarbons in Mullus surmuletus from the Catania Gulf (Sicily, Italy): distribution and potential health risks

Different specimens of Mullus surmuletus from the Catania Gulf (Sicily) were sampled and analysed for the quantification of 16 priority polycyclic aromatic hydrocarbons (PAHs) in order to evaluate the distribution of these pollutants and the potential human health risks associated to the consumption of fish. The determined PAHs concentration values ranged from 0.25 to 6.10 ng/g wet weight and the most abundant PAHs detected were lower molecular weight (LMW) compounds with 2 to 3 rings. Relying on the PAHs concentration values, on the consumption data and on the total toxic equivalent (TEQ), the incremental lifetime cancer risk (ILCR) was assessed and its calculated value (2.97 × 10−7) is far below the “maximum acceptable risk level” (ARL), suggesting a low potential carcinogenic risk on consuming M. surmuletus for local population. Even though the study shows a quite low contamination level in M. surmuletus, intensive monitoring programmes are still highly needed in order to provide a better picture of the PAHs distribution in Catania Gulf and of the human health risk linked to fish consumption.

Assessing the spatiotemporal persistence of fish distributions: a case study on two red mullet species (Mullus surmuletus and M. barbatus) in the western Mediterranean

Understanding the spatiotemporal persistence of fish distributions is key to defining fish hotspots and effective fisheries-restricted areas (FRAs). Hierarchical Bayesian spatiotemporal models provide an excellent framework to understand these distributions, as they can accommodate different spatiotemporal behaviour in the data, primarily due to their flexibility. The aim of this research was to characterize the fundamental behavioural patterns of fish as persistent, opportunistic or progressive by comparing different spatiotemporal model structures in order to provide better information for marine spatial planning. To illustrate this method, the spatiotemporal distributions of 2 sympatric Mullidae species, the striped red mullet Mullus surmuletus and the red mullet M. barbatus, were analysed. The occurrence of each species, its conditional-to-presence abundance and median length were analysed using Mediterranean trawl survey data from the western Mediterranean between 2000 and 2016. Results demonstrate that there are various common hotspots of both species distributed along the Iberian coast. The convenient persistent spatiotemporal distribution of these hotspots facilitates the configuration of a network of connected FRAs for red mullets in the study area.