Dentex dentex Frauds: Establishment of a New DNA Barcoding Marker

The common dentex (Dentex dentex (Linnaeus, 1758)) is an iconic fish in the Mediterranean diet. Due to its commercial and organoleptic importance, this sparid is highly appreciated in European markets and is often subjected to species substitution frauds. Comparative mitogenomics is a suitable approach for identifying new and effective barcode markers. This study aimed to find a molecular tag useful for unequivocally discriminating the sparid species D. dentex. The comparison of the complete mitochondrial DNA (mtDNA) sequences of 16 sparid species allowed us to highlight the potential of the NAD2 gene for direct identification purposes. Common dentex-specific primers were created and successfully evaluated by end-point and real-rime PCR (Polymerase Chain Reaction) for several fish species, achieving amplification only in the D. dentex. The method proposed in this study appears fast, simple, and inexpensive and requires affordable instrumentation. This approach provides unambiguous results for the common dentex authentication without the sequencing step. The presence/absence assay for D. dentex can be executed in a few hours of lab work. Therefore, national authorities responsible for food safety and traceability could apply and make full use of DNA-testing methods for deterring operators from false seafood declarations.

Ichthyological Hapax Legomena in Marcellus’ "De piscibus"

Marcellus of Side, a physician and didactic poet of the second century AD, mentions fourteen exclusive ichthyonyms in the preserved fragment De piscibus, extracted from the 42-volume epic poem entitled Cheironides. The author discusses Greek names of fish and sea animals that appear only in Marcellus’ work. They belong to the so-called hapax legomena. The following appellatives are carefully analyzed: ἁλιπλεύμων, ἅρπη, βούφθαλμος, βράχατος, γαρίσκος, γερῖνος, ἐρυθρός, θρανίας, θῦρος, κόλλουρος, περόνη, τραγίσκος, τυφλῖνος, χρύσοφος. It is assumed that Marcellus of Side introduced a number of ichthyonyms of Pamphylian origin, e.g. Pamph. θῦρος (< *θύρσος), βράχατος (instead of βάτραχος), ἐρυθρός (= ἐρυθρῖνος), θρανίας (instead of θράνις), χρύσοφος (instead of χρύσοφρυς). Also new identifications of fish are suggested, e.g. Gk. βούφθαλ- μος ‘large-eye dentex, Dentex macrophthalmus Bloch’, Gk. κόλλουρος ‘slender sunfish, Ranzania laevis Pennant’. All the discusssed ichthyonyms, as well as names of other sea animals, are explained from the point of view of phonology, morphology or semantics, e.g. ἁλιπλεύμων ‘jellyfish’ (literally ‘sea lung’), ἅρπη ‘a kind of ray fish’ (literally ‘a kite’).

Data mining on YouTube reveals fisher group-specific harvesting patterns and social engagement in recreational anglers and spearfishers

We applied data mining on YouTube videos to better understand recreational fisheries targeting common dentex (Dentex dentex), an iconic species of Mediterranean fisheries. In Italy alone, from 2010 to 2016 spearfishers posted 1051 videos compared to 692 videos posted by anglers. The upload pattern of spearfishing videos followed a seasonal pattern with peaks in July, a trend not found for anglers. The average mass of the fish declared in angling videos (6.4 kg) was significantly larger than the one in spearfishing videos (4.5 kg). Videos posted by spearfishers received significantly more likes and comments than those posted by anglers. Content analysis suggested that the differences in engagement can be related to appreciation of successful spearfishers necessitating relevant personal qualities for catching D. dentex. We also found that the mass of the fish positively predicted social engagement as well as the degree of positive evaluation only in spearfishing videos. This could be caused by the generally smaller odds of catching large D. dentex by spearfishing. Our case study demonstrates that data mining on YouTube can be a powerful tool to provide complementary data on controversial and data-poor aspects of recreational fisheries and contribute to understanding the social dimensions of recreational fishers.

Data mining on YouTube reveals fisher group-specific harvesting patterns and social engagement in recreational anglers and spearfishers

Data about recreational fisheries are scarce in many areas of the world. In the absence of monitoring data collected in situ, alternative data sources, such as digital applications and social media platforms, have the potential to produce valuable insights. Yet, the potential of social media for drawing insights about recreational fisheries is still underexplored. In this study, we applied data mining on YouTube videos to better understand recreational fisheries targeting common dentex (Dentex dentex), an iconic species of Mediterranean recreational fisheries. We chose this model species because of ongoing controversies about the relative impact of recreational angling and recreational spearfishing on its conservation status. In Italy alone, from 2010 to 2016 recreational spearfishers posted 1051 videos compared to 692 videos posted by recreational anglers. Only the upload pattern of spearfishing videos followed a seasonal pattern with peaks in July, suggesting seasonality of spearfishing catches of D. dentex – a trend not found for anglers. The average mass of the fish declared in recreational angling videos (6.43 kg) was significantly larger than the one in spearfishing videos (4.50 kg). Videos posted by recreational spearfishers received significantly more likes and comments than those posted by recreational anglers, suggesting that the social engagement among recreational spearfishers was stronger than in anglers. We also found that the mass of the fish positively predicted social engagement in recreational spearfishing videos, but not in videos posted by recreational anglers. This could be caused by the generally smaller odds of catching large D. dentex by spearfishing, possibly explaining why posting videos with particularly large specimen triggered larger social engagement by recreational spearfishers. Our case study demonstrates that data mining on YouTube can be a powerful tool to provide complementary data on controversial and data-poor aspects of recreational fisheries.