Fish mislabelling in France: substitution rates and retail types

Molecular Barcoding: A Tool to Guarantee Correct Seafood Labelling and Quality and Preserve the Conservation of Endangered Species

The recent increase in international fish trade leads to the need for improving the traceability of fishery products. In relation to this, consistent monitoring of the production chain focusing on technological developments, handling, processing and distribution via global networks is necessary. Molecular barcoding has therefore been suggested as the gold standard in seafood species traceability and labelling. This review describes the DNA barcoding methodology for preventing food fraud and adulteration in fish. In particular, attention has been focused on the application of molecular techniques to determine the identity and authenticity of fish products, to discriminate the presence of different species in processed seafood and to characterize raw materials undergoing food industry processes. In this regard, we herein present a large number of studies performed in different countries, showing the most reliable DNA barcodes for species identification based on both mitochondrial (COI, cytb, 16S rDNA and 12S rDNA) and nuclear genes. Results are discussed considering the advantages and disadvantages of the different techniques in relation to different scientific issues. Special regard has been dedicated to a dual approach referring to both the consumer's health and the conservation of threatened species, with a special focus on the feasibility of the different genetic and genomic approaches in relation to both scientific objectives and permissible costs to obtain reliable traceability.

Microsatellites as Molecular Markers with Applications in Exploitation and Conservation of Aquatic Animal Populations

A large number of species and taxa has been studied for genetic polymorphism. Microsatellites have been known as hypervariable neutral molecular markers with the highest resolution power in comparison with any other markers. However, the discovery of a new type of molecular marker—single nucleotide polymorphism (SNP) has put the existing applications of microsatellites to the test. To ensure good resolution power in studies of populations and individuals, a number of microsatellite loci from 14 to 20 was often used, which corresponds to about 200 independent alleles. Recently, these numbers have tended to be increased by the application of genomic sequencing of expressed sequence tags (ESTs), and the choice of the most informative loci for genotyping depends on the aims of research. Examples of successful applications of microsatellite molecular markers in aquaculture, fisheries, and conservation genetics in comparison with SNPs have been summarized in this review. Microsatellites can be considered superior markers in such topics as kinship and parentage analysis in cultured and natural populations, the assessment of gynogenesis, androgenesis and ploidization. Microsatellites can be coupled with SNPs for mapping QTL. Microsatellites will continue to be used in research on genetic diversity in cultured stocks, and also in natural populations as an economically advantageous genotyping technique.

The 11 sins of seafood: Assessing a decade of food fraud reports in the global supply chain

Due to complex, valuable, and often extremely opaque supply chains, seafood is a commodity that has experienced a high prevalence of food fraud throughout the entirety of its logistics network. Fraud detection and prevention require an in-depth understanding of food supply chains and their vulnerabilities and risks so that food business operators, regulators, and other stakeholders can implement practical countermeasures. An analysis of historical criminality within a sector, product, or country is an important component and has not yet been conducted for the seafood sector. This study examines reported seafood fraud incidents from the European Union's Rapid Alert System for Food and Feed, Decernis's Food Fraud Database, HorizonScan, and LexisNexis databases between January 01, 2010 and December 31, 2020. Illegal or unauthorized veterinary residues were found to be the most significant issue of concern, with most reports originating from farmed seafood in Vietnam, China, and India. For internationally traded goods, border inspections revealed a significant frequency of reports with fraudulent or insufficient documentation, indicating that deceptive practices are picked up at import or export but are occurring further down the supply chain. Practices such as species adulteration (excluding veterinary residues), species substitution, fishery substitution, catch method fraud, and illegal, unreported, and unregulated fishing were less prevalent in the databases than evidenced in the scientific literature. The analysis demonstrates significant differences in outcomes depending on source and underlines a requirement for a standardized and rigorous dataset through which food fraud can be scrutinized to ensure enforcement, as well as industry and research resources are directed accurately. Practical Application: Levels of historic food fraud in a product, sector, supply chain node or geographic location provide an indication of historic criminality, the methods used and the location of reported frauds. This study provides an overview of historic levels of seafood fraud that can be used to inform seafood fraud prevention and mitigation activities by the food industry, regulators and other stakeholders.

Detection and identification of marine fish mislabeling in Guangzhou's supermarkets and sushi restaurants using DNA barcoding

In this study, DNA barcoding was applied to identify the distinct species of fish products in Guangzhou supermarkets and sushi restaurants in order to confirm whether products were correctly labeled. Samples were analyzed using mitochondrial cytochrome C oxidase subunit I (CO I) gene as the target. Our results showed that the CO I gene of all 139 samples examined was successfully amplified by PCR. When sequenced, 30 samples (21.58%) were mislabeled as the wrong species, 11 samples had insufficient information provided on the label to determine if the labeling was correct (7.91%), and four samples failed sequencing (2.88%). We also found that the use of proper labels for fish products in sushi restaurants was higher than that in supermarkets. As a simple, rapid, and efficient technology, DNA barcoding can be widely used for species identification of fish products. Our work shows that regulation of the labeling of fish products, as we evaluated in Guangzhou and other markets in China, is needed on a global scale.

The Importance of Citizen Scientists in the Move Towards Sustainable Diets and a Sustainable Food System

To enhance sustainability, the food system requires significant shifts in the production, processing and supply of food. Ideally, a sustainable food system should operate, not only to protect the biosphere, but also to provide nutritious, high-quality food, and to support social values, an equitable economy, and human and animal health. It should also be governed responsibly within a supportive policy environment. Implementing these shifts is a task of immense scale; but citizen participation/engagement has the potential to help make sustainability a reality through distributed learning, dynamic sensing, and knowledge generation. Technological advancements in sensing and data processing have enabled new forms of citizen participation in research. When food system research is embedded within society it can help us to understand which changes towards sustainability work and which do not. Indeed, citizen engagement in food systems research has the potential to help bring citizens on side, supporting the growth of a food culture of resilience and of sustainable practises (including dietary change). This commentary provides examples of how existing research and alternative food production systems and agroecological practises may provide possible frameworks for citizen participation in food system studies. We highlight potential future food and citizen science approaches. Widening citizen participation and encouraging the involvement of other food system actors, including those in local, national and international governance, is essential to capture the full potential of citizen science in enabling transition to a sustainable food system. For the research community citizen science offers engagement and empowerment of wider communities with science; collecting and analysing data; and creating viable solutions to food system and diet issues.

Bioinformatics Approach to Mitigate Mislabeling in EU Seafood Market and Protect Consumer Health

Fisheries products are some of the most traded commodities world-wide and the potential for fraud is a serious concern. Fish fraud represents a threat to human health and poses serious concerns due to the consumption of toxins, highly allergenic species, contaminates or zoonotic parasites, which may be present in substituted fish. The substitution of more expensive fish by cheaper species, with similar morphological characteristics but different origins, reflects the need for greater transparency and traceability upon which which the security of the entire seafood value-chain depends. Even though EU regulations have made significant progress in consumer information by stringent labelling requirements, fraud is still widespread. Many molecular techniques such as DNA barcoding provide valuable support to enhance the Common Fisheries Policy (CFP) in the protection of consumer interests by unequivocally detecting any kind of fraud. This paper aims to highlight both the engagement of EU fishery policy and the opportunity offered by new biotechnology instruments to mitigate the growing fraud in the globalized fish market and to enforce the food security system to protect consumers' health. In this paper, after a presentation of EU rules on fish labeling and a general overview on the current state of the global fish market, we discuss the public health implications and the opportunities offered by several techniques based on genetics, reporting a case study to show the efficacy of the DNA barcoding methodology in assessing fish traceability and identification, comparing different species of the Epinephelus genus, Mottled Grouper (Mycteroperca rubra) and Wreckfish (Polyprion americanus), often improperly sold with the commercial name of "grouper".

DNA Analysis Detects Different Mislabeling Trend by Country in European Cod Fillets

Atlantic cod, Gadus morhua, is a highly appreciated fish in European seafood markets and is one of the most substituted fish species in the world. Fraud have been detected in European markets in the last decade, finding different substitute species sold as G. morhua or Atlantic cod on the label. In this study, we analyzed 252 samples of fresh and frozen cod fillets sold in Germany, the Netherlands, and France using DNA barcoding. Different trends were found in different countries: while the level of mislabeling found in Germany and the Netherlands remained at zero in the last years, a significant increase was found in the French markets comparing the current results with previous studies on fillets in France. On the one hand, this mislabeling proves the need to encourage European efforts to control seafood authenticity; on the other, zero mislabeling in two countries shows the success of current European regulations.

Illegal, Unreported, and Unregulated Fisheries Threatening Shark Conservation in African Waters Revealed from High Levels of Shark Mislabelling in Ghana

Mislabelling of fish and fish products has attracted much attention over the last decades, following public awareness of the practice of substituting high-value with low-value fish in markets, restaurants, and processed seafood. In some cases, mislabelling includes illegal, unreported, and unregulated (IUU) fishing, contributing to overexploit substitute species that are undetectable when sold under wrong names. This is the first study of DNA barcoding to assess the level of mislabelling in fish marketed in Ghana, focusing on endangered shark species. Genetic identification was obtained from 650 base pair sequences within the cytochrome c oxidase I (COI) gene. All except one of 17 shark fillets analysed were wrongly labelled as compared with none of 28 samples of small commercial pelagic fish and 14 commercial shark samples purchased in Europe. Several substitute shark species in Ghana are endangered (Carcharhinus signatus and Isurusoxyrinchus) and critically endangered (Squatina aculeata). Shark products commercialized in Europe (n = 14) did not reveal mislabelling, thus specific shark mislabelling cannot be generalized. Although based on a limited number of samples and fish markets, the results that reveal trade of endangered sharks in Ghana markets encourage Ghanaian authorities to improve controls to enforce conservation measures.

Identification and semi-quantification of Atlantic salmon in processed and mixed seafood products using Droplet Digital PCR (ddPCR)

Fishery products are often subject to substitution fraud, which is hard to trace due to a lack of morphologic traits when processed, gutted, or decapitated. Traditional molecular methods (DNA barcoding) fail to identify products containing multiple species and cannot estimate original weight percentages. As a proof of concept, an Atlantic salmon (Salmo salar) specific ddPCR assay was designed to authenticate mixed food products. The method proved to be specific and able to accurately quantify S. salar when using DNA extracts, even in the presence of DNA from closely related salmon species. The ddPCR estimates correlated well with the percentage of S. salar in artificially assembled tissue mixtures. The effect of common salmon processing techniques (freezing, smoking, poaching with a "Bellevue" recipe and marinating with a 'Gravad lax' recipe) on the ddPCR output was investigated and freezing and marinating appeared to lower the copies detected by the ddPCR. Finally, the assay was applied to 46 retail products containing Atlantic or Pacific salmon, and no indications of substitution fraud were detected. The method allows for a semi-quantitative evaluation of the S. salar content in processed food products and can rapidly screen Atlantic salmon products and flag potentially tampered samples for further investigation.

Geographic Pattern of Sushi Product Misdescription in Italy-A Crosstalk between Citizen Science and DNA Barcoding

The food safety of sushi and the health of consumers are currently of high concern for food safety agencies across the world due to the globally widespread consumption of these products. The microbiological and toxicological risks derived from the consumption of raw fish and seafood have been highlighted worldwide, while the practice of species substitution in sushi products has attracted the interest of researchers more than food safety agencies. In this study, samples of sushi were processed for species authentication using the Cytochrome Oxidase I (COI) gene as a DNA barcode. The approach of Citizen Science was used to obtain the sushi samples by involving people from eighteen different Italian cities (Northern, Central and Southern Italy). The results indicate that a considerable rate of species substitution exists with a percentage of misdescription ranging from 31.8% in Northern Italy to 40% in Central Italy. The species most affected by replacement was Thunnus thynnus followed by the flying fish roe substituted by eggs of Mallotus villosus. These results indicate that a standardization of fish market names should be realized at the international level and that the indication of the scientific names of species should be mandatory for all products of the seafood supply chain.

Chilean Salmon Sushi: Genetics Reveals Product Mislabeling and a Lack of Reliable Information at the Point of Sale

Species diagnosis is essential to assess the level of mislabeling or misnamed seafood products such as sushi. In Chile, sushi typically includes salmon as the main ingredient, but species used are rarely declared on the menu. In order to identify which species are included in the Chilean sushi market, we analyzed 84 individual sushi rolls sold as "salmon" from sushi outlets in ten cities across Chile. Using a polymerase chain reaction-restriction fragment length polymorphism protocol (PCR-RFLP), we identified mislabeled and misnamed products. Atlantic salmon was the most common salmonid fish used in sushi, followed by coho salmon, rainbow trout, and Chinook salmon. We found a total of 23% and 18% of the products were mislabeled and misnamed, respectively. In 64% of cases, the salesperson selling the product could not identify the species. We also identified the use of wild-captured Chinook salmon samples from a naturalized population. Our results provide a first indication regarding species composition in Chilean sushi, a quantification of mislabeling and the level of misinformation declared by sales people to consumers. Finally, considering that Chinook salmon likely originates from a non-licensed origin and that sushi is an uncooked product, proper identification in the food production chain may have important consequences for the health of consumers.

DNA-based techniques for seafood species authentication

Global trade of seafood has increased in the last decade, leading to significant concerns associated with seafood fraud. Seafood fraud involves the intentional misrepresentation of fish or shellfish for the purpose of economic gain and includes acts such as species substitution, illegal transshipment, overtreatment/short weighting, and mislabeling country of origin or production method. These fraudulent acts have had economic, environmental, and public health consequences on a global level. DNA-based techniques for seafood authentication are utilized by regulatory agencies and can be employed as part of a food fraud risk mitigation plan. This chapter will focus specifically on the use of DNA-based methods for the detection of seafood species substitution. Various methods have been developed for DNA-based species identification of seafood, including polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), species-specific PCR, real-time PCR, Sanger sequencing, microarrays, and high-resolution melting (HRM). Emerging techniques for seafood authentication include droplet digital PCR, isothermal amplification, PCR-enzyme-linked immunosorbent assay (ELISA), and high-throughput or next-generation sequencing. Some of these DNA-based methods target specific species, such as real-time PCR and droplet digital PCR, while other methods allow for simultaneous differentiation of a wide range of fish species, including Sanger sequencing and high-throughput sequencing. This chapter will begin with an introduction on seafood fraud and species substitution, followed by an analysis of the main DNA-based authentication methods and emerging techniques for species identification.

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.

A high-quality genetic reference database for European commercial fishes reveals substitution fraud of processed Atlantic cod (Gadus morhua) and common sole (Solea solea) at different steps in the Belgian supply chain

Seafood is an important component of the human diet. With depleting fish stocks and increasing prices, seafood is prone to fraudulent substitution. DNA barcoding has illustrated fraudulent substitution of fishes in retail and restaurants. Whether substitution also occurs in other steps of the supply chain remains largely unknown. DNA barcoding relies on public reference databases for species identification, but these can contain incorrect identifications. The creation of a high quality genetic reference database for 42 European commercially important fishes was initiated containing 145 Cytochrome c oxidase subunit I (COI) and 152 Cytochrome b (cytB) sequences. This database was used to identify substitution rates of Atlantic cod (Gadus morhua) and common sole (Solea solea) along the fish supply chain in Belgium using DNA barcoding. Three out of 132 cod samples were substituted, in catering (6%), import (5%) and fishmongers (3%). Seven out of the 41 processed sole samples were substituted, in wholesale (100%), food services (50%), retailers (20%) and catering (8%). Results show that substitution of G. morhua and S. solea is not restricted to restaurants, but occurs in other parts of the supply chain, warranting for more stringent controls along the supply chain to increase transparency and trust among consumers.

Swordfish or Shark Slice? A Rapid Response by COIBar-RFLP

Market transparency is in strong demand by consumers, and the authentication of species is an important step for seafood traceability. In this study, a simple molecular strategy, COIBar–RFLP (cytochrome oxidase I barcode–restriction fragment length polymorphism), is proposed to unveil commercial fraud based on the practice of species substitution in the swordfish trade. In particular, COI barcoding allowed the identification of the species Prionace glauca, Mustelus mustelus, and Oxynotus centrina in slices labeled as Xiphias gladius. Furthermore, the enzymatic digestion of COI amplicons using the MboI restriction endonuclease allowed the simultaneous discrimination of the four species. Interestingly, an intraspecific differential MboI pattern was obtained for the swordfish samples. This pattern was useful to differentiate the two different clades revealed in this species by phylogenetic analyses using several molecular markers. These results indicate the need to strengthen regulations and define molecular tools for combating the occurrence of fraud along the seafood supply chain and show that COIBar–RFLP could become a standardized molecular tool to assess seafood authenticity.

From Fish Eggs to Fish Name: Caviar Species Discrimination by COIBar-RFLP, an Efficient Molecular Approach to Detect Fraud in the Caviar Trade

The demand for caviar is growing as is its price on the market. Due to the decline of true caviar production from sturgeons, eggs from other fish species and other animals have been used as substitutes for caviar. The labels on these products should indicate the species from which the eggs were derived, but the label can be misleading in some cases. In this context, species identification using DNA analysis is crucial for traceability and authentication of caviar products. In this work, we applied the COIBar-RFLP procedure to obtain species-specific endonuclease restriction patterns useful to discriminate “caviar” species. The tested caviar products were identified as originating from eight species: Acipenser transmontanus, A. gueldenstaedtii, A. stellatus, A. baerii, Mallotus villosus, Huso huso, Cyclopterus lumpus and Eumicrotremus orbis. The results demonstrated that 14% of the caviar products examined have a label that does not indicate the species from which the eggs were originated. The MboI restriction enzyme produced specific profiles discriminating the eight species, confirming that the COIBar-RFLP is a useful approach for routine screening of seafood products due to its ease and rapid execution, as the results of screening can be obtained within 7 h, by-passing the need for sequencing.

Tuna labels matter in Europe: Mislabelling rates in different tuna products

Tuna fisheries and processing represent economic activities of paramount importance around the world. Most of these products are traded for human consumption and in general are highly demanded commodities. However, not all tuna products achieve the same market price, some consumers are willing to pay a huge amount of money for certain species (i.e. Japanese market for Bluefin tuna) while other species are rather affordable (i.e. Skipjack tuna), therefore mislabelling has been observed frequently. We collected and analysed 545 tuna samples in six European countries, including fresh, frozen and canned products, and we have investigated whether or not these products were correctly labelled under European and national legislations. We found an overall mislabelling rate of 6.79%; in particular, 6.70% of the fresh and frozen tuna products and 7.84% of canned tuna were mislabelled, and only in the case of fresh and frozen tuna samples significant differences among countries were found. Mislabelling rates for Atlantic Bluefin tuna labelled products were very high, ranging from 50 up to 100%. In general, mislabelling was higher when specific names were included in the labels. The “tuna” umbrella term is a very popular one with consumers, but also one that remains vulnerable to ambiguity, hampering efforts towards market transparency and with potential negative consequences to the adequate management of tuna species stocks.

DNA barcode identification of commercial fish sold in Mexican markets

The substitution of high-value fish species for those of lower value is common practice. Although numerous studies have addressed this issue, few have been conducted in Mexico. In this study, we sought to identify fresh fillets of fish, sharks, and rays using DNA barcodes. We analyzed material from "La Viga" in Mexico City, and other markets located on the Gulf and Caribbean coasts of Mexico. From 134 samples, we obtained sequences from 129, identified to 9 orders, 28 families, 38 genera, and 44 species. The most common species were Seriola dumerili, Pangasianodon hypophthalmus, Carcharhinus falciformis, Carcharhinus brevipinna, and Hypanus americanus. Pangasianodon hypophthalmus was most commonly used as a substitute for higher-value species. The substitution rate was 18% of the total. A review of the conservation status of the specimens identified against the IUNC list enabled us to establish that some species marketed in Mexico are threatened: Makaira nigricans, Lachnolaimus maximus, Hyporthodus flavolimbatus, and Isurus oxyrinchus are classified as vulnerable; Lopholatilus chamaeleonticeps and Sphyrna lewini are endangered; and the status of Hyporthodus nigritus is critical. These results will demonstrate to the Mexican authorities that DNA barcoding is a reliable tool for species identification, even when morphological identification is difficult or impossible.

Using DNA barcoding to track seafood mislabeling in Los Angeles restaurants

Seafood mislabeling is common in both domestic and international markets. Studies on seafood fraud often report high rates of mislabeling (e.g., >70%), but these studies have been limited to a single sampling year, which means it is difficult to assess the impact of stricter governmental truth-in-labeling regulations. We used DNA barcoding to assess seafood labeling in 26 sushi restaurants in Los Angeles over 4 years. Seafood from 3 high-end grocery stores were also sampled (n = 16) in 2014. We ordered 9 common sushi fish from menus, preserved tissue samples in 95% ethanol, extracted the genomic DNA, amplified and sequenced a portion of the mtDNA COI gene, and identified the resulting sequence to known fish sequences from the National Center for Biotechnology Information nucleotide database. We compared DNA results with the U.S. Food and Drug Administration (FDA) list of acceptable market names and retail names. We considered sushi-sample labels that were inconsistent with FDA names mislabeled. Sushi restaurants had a consistently high percentage of mislabeling (47%; 151 of 323) from 2012 to 2015, yet mislabeling was not homogenous across species. Halibut, red snapper, yellowfin tuna, and yellowtail had consistently high (<77%) occurrences of mislabeling on menus, whereas mislabeling of salmon and mackerel were typically low (>15%). All sampled sushi restaurants had at least one case of mislabeling. Mislabeling of sushi-grade fish from high-end grocery stores was also identified in red snapper, yellowfin tuna, and yellowtail, but at a slightly lower frequency (42%) than sushi restaurants. Despite increased regulatory measures and media attention, we found seafood mislabeling continues to be prevalent.

Development of a MALDI-TOF MS-Based Protein Fingerprint Database of Common Food Fish Allowing Fast and Reliable Identification of Fraud and Substitution

Fish substitution and fish fraud are widely observed in the global food market. To detect and prevent substitution, DNA-based methods do not always meet the demand of being time- and cost-efficient; therefore, methodology improvements are needed. The use of species-specific protein patterns, as determined by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, has recently improved species identification of prokaryotes both time- and cost-wise. We used the method to establish a database containing protein patterns of common food fish prone to substitution. The database currently comprises 54 fish species. Aspects such as the sensitivity of identification on the species level and the impact of bacterial contamination of fish filets are assessed. Most database entries are characterized by low intraspecies but high interspecies variability. Hitherto, 118 validation samples were successfully determined. The results presented herein underline the potential and reliability of eukaryotic species identification via MALDI-TOF mass spectrometry.

Heavy metal content and molecular species identification in canned tuna: Insights into human food safety

Canned tuna in olive oil and in brine of the most popular brands sold in Italian markets were analyzed to verify the authentication of transformed products, with the aim to unveil commercial frauds due to the substitutions of high value species with species of low commercial value, and to assess the health risk of consumers related to cadmium (Cd), lead (Pb) and mercury (Hg) contents. Species authentication was evaluated with amplification of COI DNA barcode and confirmed the declared species. Among tested metals, Hg had the highest concentrations, followed by Cd and Pb. None of the tested samples surpassed the European regulatory limits no. 1881/2006 fixed for Hg and Pb, whereas one batch of canned tuna in olive oil exceeded standard for Cd. Risk for human health was evaluated by the metals daily intake and target hazard quotient (THQ). As a result, Cd and Pb did not exceed the toxicological reference values established by World Health Organization (WHO) and the Environmental Protection Agency (EPA). Conversely, Hg content suggests a consumption no more than once a week and a continuous surveillance of this fishery products for consumer protection.

Development of a qPCR Method for the Identification and Quantification of Two Closely Related Tuna Species, Bigeye Tuna (Thunnus obesus) and Yellowfin Tuna (Thunnus albacares), in Canned Tuna

Bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) are among the most widely used tuna species for canning purposes. Not only substitution but also mixing of tuna species is prohibited by the European regulation for canned tuna products. However, as juveniles of bigeye and yellowfin tunas are very difficult to distinguish, unintentional substitutions may occur during the canning process. In this study, two mitochondrial markers from NADH dehydrogenase subunit 2 and cytochrome c oxidase subunit II genes were used to identify bigeye tuna and yellowfin tuna, respectively, utilizing TaqMan qPCR methodology. Two different qPCR-based methods were developed to quantify the percentage of flesh of each species used for can processing. The first one was based on absolute quantification using standard curves realized with these two markers; the second one was founded on relative quantification with the universal 12S rRNA gene as the endogenous gene. On the basis of our results, we conclude that our methodology could be applied to authenticate these two closely related tuna species when used in a binary mix in tuna cans.

Tuna Species Substitution in the Spanish Commercial Chain: A Knock-On Effect

Intentional mislabelling of seafood is a widespread problem, particularly with high-value species like tuna. In this study we examine tuna mislabelling, deliberate species substitution, types of substitution and its impact on prices. The survey covered the commercial chain, from Merca-Barna to fishmongers and restaurants in the Spanish Autonomous Community of Catalonia. To understand the geographic extent of the problem we also sampled Merca-Madrid, Europe's biggest fish market, and Merca-Málaga for its proximity to the bluefin tuna migratory route and trap fishery. Monthly surveys were carried out over one year. The results showed a high deficiency in labelling: 75% of points of sale and 83% of restaurants did not specify the species, and in those cases the name of the species had to be asked. A total of 375 samples were analysed genetically, the largest dataset gathered in Europe so far. The identified species were Thunnus albacares, Thunnus thynnus and Thunnus obesus. Species substitution began at suppliers, with 40% of observed cases, increasing to 58% at fishmongers and 62% at restaurants. The substitution was mainly on bluefin tuna (T. thynnus), 73% of cases. At restaurants, only during the bluefin fishing season, we observed a decrease of Bluefin tuna substitution and an increase of reverse substitution revealing some illegal fishing. The effect of species substitution on species prices was relevant: T. obesus increased its price by around €12 kg-1 when it was sold as bluefin. In view of the deficiency of labelling, the abuse of generic names and the lack of the bluefin catch document, we conclude that the Spanish regulations are ineffective, highlighting the need for policy execution, and the urgent need for information campaigns to Spanish consumers.

A real time metabolomic profiling approach to detecting fish fraud using rapid evaporative ionisation mass spectrometry

INTRODUCTION

Fish fraud detection is mainly carried out using a genomic profiling approach requiring long and complex sample preparations and assay running times. Rapid evaporative ionisation mass spectrometry (REIMS) can circumvent these issues without sacrificing a loss in the quality of results.

OBJECTIVES

To demonstrate that REIMS can be used as a fast profiling technique capable of achieving accurate species identification without the need for any sample preparation. Additionally, we wanted to demonstrate that other aspects of fish fraud other than speciation are detectable using REIMS.

METHODS

478 samples of five different white fish species were subjected to REIMS analysis using an electrosurgical knife. Each sample was cut 8-12 times with each one lasting 3-5 s and chemometric models were generated based on the mass range m/z 600-950 of each sample.

RESULTS

The identification of 99 validation samples provided a 98.99% correct classification in which species identification was obtained near-instantaneously (≈ 2 s) unlike any other form of food fraud analysis. Significant time comparisons between REIMS and polymerase chain reaction (PCR) were observed when analysing 6 mislabelled samples demonstrating how REIMS can be used as a complimentary technique to detect fish fraud. Additionally, we have demonstrated that the catch method of fish products is capable of detection using REIMS, a concept never previously reported.

CONCLUSIONS

REIMS has been proven to be an innovative technique to help aid the detection of fish fraud and has the potential to be utilised by fisheries to conduct their own quality control (QC) checks for fast accurate results.

Authentication of Closely Related Fish and Derived Fish Products Using Tandem Mass Spectrometry and Spectral Library Matching

Proteomics methodology has seen increased application in food authentication, including tandem mass spectrometry of targeted species-specific peptides in raw, processed, or mixed food products. We have previously described an alternative principle that uses untargeted data acquisition and spectral library matching, essentially spectral counting, to compare and identify samples without the need for genomic sequence information in food species populations. Here, we present an interlaboratory comparison demonstrating how a method based on this principle performs in a realistic context. We also increasingly challenge the method by using data from different types of mass spectrometers, by trying to distinguish closely related and commercially important flatfish, and by analyzing heavily contaminated samples. The method was found to be robust in different laboratories, and 94-97% of the analyzed samples were correctly identified, including all processed and contaminated samples.

Sushi barcoding in the UK: another kettle of fish

Although the spread of sushi restaurants in the European Union and United States is a relatively new phenomenon, they have rapidly become among the most popular food services globally. Recent studies indicate that they can be associated with very high levels (>70%) of fish species substitution. Based on indications that the European seafood retail sector may currently be under better control than its North American counterpart, here we investigated levels of seafood labelling accuracy in sushi bars and restaurants across England. We used the COI barcoding gene to screen samples of tuna, eel, and a variety of other products characterised by less visually distinctive ‘white flesh’. Moderate levels of substitution were found (10%), significantly lower than observed in North America, which lends support to the argument that public awareness, policy and governance of seafood labels is more effective in the European Union. Nevertheless, the results highlight that current labelling practice in UK restaurants lags behind the level of detail implemented in the retail sector, which hinders consumer choice, with potentially damaging economic, health and environmental consequences. Specifically, critically endangered species of tuna and eel continue to be sold without adequate information to consumers.