dna barcoding (6)

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This study used DNA barcoding to identify fish species and microbiome profiling  to study the presence of pathogens. Between February 2018 and October 2020, 127 fish samples were collected from restaurants (83 samples), and the remainder (44 samples) from hypermarkets, supermarkets, markets, seafood wholesalers/retailers, and fishing harbours. The microbiological analysis was undertaken because most of the restaurant samples were raw fish sashimi/sushi. The study found that 24 of the samples were mislabelled as regards the fish species, and snapper had the largest number of mislabelled samples (11), which had been substituted by tilapia. This may be due to the labelling of tilapia as Taiwan-Snapper.

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5164616286?profile=RESIZE_400xFish species substitution and/or mislabelling is known to be a serious global issue. Spanish researchers used DNA barcoding to identify fish species in 313 samples collected in 204 mass catering outlets from 15 Spanish Autonomous Communities. The results showed that 50% of the food catering establishments sold mislabelled seafood. The fish species found to be most substituted were dusky grouper (shown left and known as Mero in Spanish) and tope shark, which were substituted by similar species of fish from Asian, South American and South African regions.

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In a follow up of a 2018 report, Oceana Canada have released a recent report on the results of a survey of 90 samples taken from 50 different locations in Montreal in 2019. The samples were sent to a commercial laboratory for testing using DNA barcoding for species identification, which found that 31 samples were a different species than was claimed, 21 were mislabelled and three contained species not authorised for sale in Canada.  The 2018 report found a mislabelling rate of 44% in samples from from 5 cities, excluding Montreal. The Montreal results, when combined with previous investigations since 2017, found 47% of the 472 fish samples to date were mislabelled in Montreal, Victoria, Vancouver, Toronto, Ottawa and Halifax.

1076187540?profile=RESIZE_710x Read the article here and also Oceana Canada's report

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Researchers from the University of Guelph in collaboration with the Canadian Food Inspection Agency (CFIA) have found high levels of fish mislabelling in the supply chain starting from imports and increasing as the supply moves along the chain to retail. The research team examined 203 samples from 12 key targeted species collected from various importers (23% of samples), processing plants (5.5%) and retailers (69.5%) in Ontario. The species of fish was identified in the samples using DNA barcoding. The results revealed that overall 32% of the 203 samples were mislabelled, with 17.6 % mislabelling at the import stage, 27.3% at processing plants and 38.1% at retailers. The authors commented that the higher mislabelling rate in samples collected from retailers, compared to that for samples collected from importers, indicates the role of distribution and repackaging in seafood mislabeling. Also, there is a lack of harmonisation in the regulatory framework between for example, Canada and the US, where there is a lack of equivalence in the commercial names given to fish species. This would be improved by giving the scientific name as well. 

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Many shark populations are in decline, primarily due to overexploitation. In response, conservation measures have been applied at differing scales, often severely restricting sales of declining species. Between February 2016 and November 2017, scientists at the University of Exeter analysed a total of 117 samples of shark meat products  collected from 90 different caterers/retailers.  Seventy eight of these were battered and fried originating from fish and chip takeaways, and 39 were either fresh or frozen and collected from fishmongers. In addition, 10 fins collected from an Asian food wholesaler, as well as 30 fins seized by the UK Border Force on their way from Mozambique to Asia were also analysed. Using  multiple extraction techniques and DNA barcoding, the species of shark in the samples were identified. As regards the fish and chip takeaways, the majority of samples were identified as spiny dogfish (Squalus acanthias), which is critically endangered in the Northeast Atlantic and landings have been prohibited. The fin samples included scalloped hammerhead sharks (Sphyrna lewini), which are endangered globally and subject to trade restrictions, and other threatened sharks such as shortfin mako and smalleye hammerhead sharks.

 Read the Press Release and the full research paper.

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The New York Attorney General's Office has just published a report of a survey into the labelling of fish species in New York's supermarket chains. Fish (snapper, grouper, cod, wild salmon, halibut, sole, striped bass and white tuna) was sampled from 155 retail  locations from 29 supermarket chains, and sent to Northeastern University for DNA testing. 27% of the samples were found to be mislabelled. A group of 5 of the supermarket chains were responsible for most of the mislabelled samples with more than 50% of their samples mislabelled. 87.5% of the lemon sole, and 67% of the red snapper were mislabelled, and 28% of the salmon was wrongly sold as wild when it was farmed. The report gives best practice for businesses to ensure that the consumer is not purchasing mislabelled fish. 

 Read the article and the full NYAG report

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