Access the full text.
Sign up today, get DeepDyve free for 14 days.
The Atlantic Cod Gadus morhua is fished in Northern Atlantic and Arctic waters. In Mexico cod is imported from Norway and the United States, and is traditionally eaten at Christmas and Easter. In Mexico City several stores sell dry-salted cod, but due to the high price of the imported Atlantic Cod, other fish species are sold. In this project we examined six samples of dried-salted fish from different stores and used DNA barcoding of the COI gene to corroborate the identity of the product sold as Atlantic Cod. Barcoding revealed that only two of the six samples (33%) were Atlantic cod, with two being Ling, one Alaska Pollock, and one Blue Shark. The high rate of mislabeling (67%) is a major concern. It is especially worrying that Blue Shark is being sold as Atlantic cod, since the Blue Shark is listed as a near-threatened species by the IUCN. We must be aware of the damages that overexploitation and uninformed consumption cause to cod and shark populations. There needs to be stricter policing of seafood product labeling in México. Keywords: Barcode, Atlantic Cod, food, shark, DNA, COI, conservation 1 Introduction Cods (Gadiformes) comprise ten families and 612 species . Gadids are marine fishes with a Holarctic distribution, attaining their greatest diversity in the Atlantic. Gadus morhua Linnaeus, 1758 (Atlantic Cod, bacalao or morue *Corresponding author: Héctor Espinosa, Colección Nacional de Peces, Instituto de Biología, Universidad Nacional Autónoma de México. Distrito Federal. 04510. México, E-mail: email@example.com Christian Lambarri, Armando Martínez, Ariana Hernández, Colección Nacional de Peces, Instituto de Biología, Universidad Nacional Autónoma de México. Distrito Federal. 04510. México franche) inhabits deep-cold waters across the North Atlantic and Arctic Oceans; more specifically it occurs along the North American coast in Canada and North Carolina in the Western Atlantic, on the east and west coast of Greenland, around Iceland, and around Bear Island along the European coast to Bay of Biscay. This species is generally fished and dried in northern countries such as Norway, Spain, France, Greenland, the United States and Canada. Due to its importance, this fish has even been called "beef of the sea" . The Atlantic Cod is the main cod species exported from the European market all over the world. Latin-American countries are the top consumers of this fish, especially during religious celebrations. The cod trade developed in the 12th century when Norwegians traveled to the rest of Europe with dried cod among their food supplies. Soon enough, the cod market developed in southern Europe and later the first Spaniards brought dried cod to America [3,4]. Since 800 AD cods have been an important commodity in the international market with the official commercialization of Gadus morhua, G. macrocephalus Tilesius 1810 (Pacific Cod), and G. ogac Richardson 1837 (Greenland Cod). According to the market needs there are some other fish that are sold as cod: the codlike Pollack (Pollachius pollachius Linnaeus 1758), the Haddock (Melanogrammus aeglefinus Linnaeus 1758), the Blue Whiting (Micromesistius poutassou (Risso 1827)), hakes (Merluccius spp), Whiting (Merlangius merlangius (Linnaeus 1758)), Cusk (Brosme brosme Ascanius 1772), Blue Ling (Molva dypterygia Pennant 1784), and Saithe or Pollock (Pollachius virens Linnaeus 1758) [5,6]. Blue Ling and Saithe are sold all over the world, especially in LatinAmerican and African markets, and Saithe is one of the cheapest commercialized fish species . The import of marine products into Mexico has a long tradition since the discovery of the Americas. Cod is imported to this country from Norway and the United States, where it is traditionally eaten at Christmas and Easter as bacalao a la Vizcaína or as Torta de bacalao. The unavailability or high price of animal or plant © 2015 Christian Lambarri et al. licensee De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. C. Lambarri et al. products has resulted in the substitution of the product for some other species that can be cheaper or easier to obtain. The high price of imported cod in Mexico resulted in the use of other species as dried-salted fish. Several studies have detected the mislabeling of fish and other seafood in different countries [8,9] and have highlighted the utility of DNA barcoding methods to detect such cases. Sequencing was done at the Instituto de Biología of the Universidad Nacional Autónoma de México. Sequence reads were assembled and edited with Finch TV Version 1.4.0 (Geospiza Research Team) [11,12]. We searched and aligned the sequences with the BOLD database (BOLDsystems) and GenBank database using a nucleotide query in BLAST . 2 Methods Samples were obtained from muscular tissue of six different dried-salted fish for sale at stores in Mexico City. The tissues were washed in distilled water for a week before extraction to remove all the remaining salt and then stored in 96% ethanol. DNA extraction was performed with the EZ-10 Spin Column Animal DNA Mini-Preps Kit (Bio Basic Canada Inc.). We corroborated the presence of DNA from the extraction process via spectrophotometer quantification with a NanoDrop 2000 UV-Vis spectrophotometer (Thermo Scientific) at a wavelength of 260 nm. We re-checked the sampling via electrophoresis in a 1.5% agarose gel. We visualized the resulting gel in a dark room with UV light and photographed the gel with a Kodak 1D camera. We assembled the samples with a negative control and performed PCR in a total volume of 25 µl. The PCR reaction included 16.375 µl of ultra-pure water, 2.5 µL 10x PCR buffer, 0.5 µL dNTPs, 1.5 µL MgCl2, 0.125 µl of TaqDNA, 1 µl of each COI primer (FishR1- FishF1 or FishR2- FishF2) designed by Ward et al. , and 2.0 µl of genomic DNA. We conducted two PCR reactions with each set of primers. The thermal cycle profile for COI consisted in a temperature of 94°C for 2 min, 35 cycles of 94°C for 30 s, 52°C for 40 s, and 72°C for 1 min, with an extension of 72°C for 10 min and a final cooling to 4°C. We visualized the PCR products on a 1.5% agarose gel and observed and photographed the gel as mentioned before. Table 1. Species sold as Atlantic Cod in Mexico City stores. Sample Baca1 Baca2 Baca3 Baca4 Baca5 Baca6 GenBank Probability Prionace glauca (Linnaeus 1758) Molva dipterygia (Pennant 1784) Molva dipterygia (Pennant 1784) Gadus morhua Linnaeus 1758 Gadus morhua Linnaeus 1758 100.0% 96.0% 91.0% 99.0% 99.0% 3 Results Our results showed that the sold dried fish is rarely Atlantic Cod, and in most cases the sold species are near threatened or incidentally fished species (Table 1). One of the most interesting species found was the Blue Shark, which is listed as Near Threatened in the IUCN red list . According to the IUCN, the Blue Shark is taken in large numbers mainly as bycatch, but there are no population estimates and many catches are unreported. The unreported catches are probably commercialized as cod. The main advantage of trading in shark meat is that unlike other fish, shark meat has no bones to vie with, which makes it easier to handle and prepare, as well as easier to slip into the national market. It was expected to find the Ling and Blue Ling among the samples, since Mexico and Latin America are one of the greatest markets for this species, but the Alaska Pollock is a cod species that had not been reported before as an importation item or as a cheap replacement of Atlantic Cod in Mexico City. As for the stock prices, all the fish were sold almost at the same price, which could mean that the stores or the importers themselves are not aware of the true fish that is being sold. 4 Discussion Since Atlantic Cod from the North Atlantic is depleted and still recovering [15-17], buyers recommend replacing Common name Blue Shark Blue Ling Blue Ling Alaska Pollock Atlantic Cod Atlantic Cod BOLD Probability Prionace glauca (Linnaeus 1758) Molva molva (Linnaeus 1758) Molva molva (Linnaeus 1758) Gadus morhua Linnaeus 1758 Unable to match 100.0% 100.0% 99.5% 99.6% - Common name Blue Shark Ling Ling Alaska Pollock Atlantic Cod Gadus chalcogrammus Pallas 1814 96.0% Gadus chalcogrammus Pallas 1814 99.8% it with other white fish such as Pacific Cod, Hoki, Hake, or even dried shark meat that fishermen sell, all of which can be less expensive. Apart from the genetic differences, Atlantic Cod has a firmer texture and slightly lower moisture content than its congeneric Pacific Cod, as well as more softness than shark meat. Therefore there would be no reason for consumers to prefer or even detect a difference in the consistency or flavor of fish, since the lack of water and excess of salt mask them both. Nevertheless, consumers need to be aware of the damages that the overexploitation and uninformed consumption can cause to cod and shark populations, especially if we consider the consequences of previous cod wars and overexploitation cases, in which Manley  fairly stated that "The only sure losers in this game are the cod!", although it is obvious that there are plenty of environmental and economic losses through the mislabeling of products. Product mislabeling can be the result of true mistakes or even fraud, but in both cases it directly affects the consumer in that they pay for something that is being replaced. In a country in which Cod consumption is so culturally rooted it is important to know the actual product that consumers are buying. It is obvious that the economic needs and the ease of trading the bycatch or unreported species facilitate the consumption of fish that are neither liked nor voluntarily bought by people. Therefore, people and government inspectors need to find a way to assure the identity of consumer products. The Barcode of Life offers the possibility to guarantee the identity and fair price of traded products. Acknowledgements: We thank the project Red Temática CONACYT Mex-Bol for support and funding. We also thank A. Jiménez from the molecular laboratory and L. Márquez from the laboratory of DNA Sequencing of the Instituto de Biología of the Universidad Nacional Autónoma de México for their active help in the molecular laboratory facilities. We thank Dr. M. Valdez-Moreno and M. Elias for the support and invitation to participate in the Second International Conference on DNA Barcoding of Fishes held in Chetumal city in September 2014. Finally we want to thank the reviewers for their important contributions and improvement of the manuscript. Conflict of interest: Authors declare nothing to disclose
DNA Barcodes – de Gruyter
Published: Jan 1, 2015
Access the full text.
Sign up today, get DeepDyve free for 14 days.