Application of DNA‐Based Methods to Identify Fish and Seafood Substitution on the Commercial Market

ABSTRACT: Fish and seafood substitution has become an important concern in domestic and international marketplaces, in part due to increased international trade, per capita seafood consumption, and production of processed foods. In many cases, seafood substitution is a form of economic deception, where highly prized species are substituted with those of lesser value. To prevent illegal species substitution, a number of DNA‐based methods have been developed to detect fish and seafood species in commercial products. These methods, along with common gene targets, have been reviewed previously in this journal. The current article is meant to build upon earlier discussions by providing a comprehensive review of the application of these DNA‐based methods to the discovery of fish and seafood substitution on the commercial market. Popular food uses, potential substitution cases, and peer‐reviewed research articles published to date are discussed for all major species groups of concern, including flatfish, gadoids, scombroids, salmonids, percoids, sturgeons, sharks, eels, and bivalves. The use of DNA‐based methods to monitor commercial whale meat products is also reviewed.     

Risk‐Benefit Analysis of Seafood Consumption: A Review

Abstract: Seafood, defined here as marine and freshwater fish and shellfish, is recognized as a healthy food choice because it is a low‐fat protein source that provides long‐chain omega‐3 fatty acids important for early development along with eye and heart health. However, seafood is also known to contain certain contaminants, such as methylmercury and persistent organic pollutants, which can have harmful effects on human health and development. In order to limit exposure to contaminants while maximizing the benefits of seafood consumption, a number of quantitative and qualitative risk‐benefit analyses have been conducted for seafood consumption. This review paper provides a brief background on risk‐benefit analysis of foods, followed by a discussion of the risks and benefits associated with fish consumption. Next, risk‐benefit analyses are reviewed in an historical context. While risk‐benefit analysis consists of three main elements (that is, assessment, management, and communication), this review will primarily focus on risk‐benefit assessments. Overall, most studies have found that the benefits far outweigh the risks among the general population, especially when a variety of fish is consumed at least twice per week. However, for certain populations (for example, pregnant women and young children) a more targeted approach is warranted in order to ensure that these groups consume fish that are low in contaminants but high in omega‐3 fatty acids. The potentially harmful unintended consequences of risk‐benefit communication on the general population and certain groups are also discussed.     

A multiplex PCR method for the identification of commercially important salmon and trout species (Oncorhynchus and Salmo) in North America

Abstract: The purpose of this study was to develop a species-specific multiplex polymerase chain reaction (PCR) method that allows for the detection of salmon species substitution on the commercial market. Species-specific primers and TaqMan® probes were developed based on a comprehensive collection of mitochondrial 5′ cytochrome c oxidase subunit I (COI) deoxyribonucleic acid (DNA) “barcode” sequences. Primers and probes were combined into multiplex assays and tested for specificity against 112 reference samples representing 25 species. Sensitivity and linearity tests were conducted using 10-fold serial dilutions of target DNA (single-species samples) and DNA admixtures containing the target species at levels of 10%, 1.0%, and 0.1% mixed with a secondary species. The specificity tests showed positive signals for the target DNA in both real-time and conventional PCR systems. Nonspecific amplification in both systems was minimal; however, false positives were detected at low levels (1.2% to 8.3%) in conventional PCR. Detection levels were similar for admixtures and single-species samples based on a 30 PCR cycle cut-off, with limits of 0.25 to 2.5 ng (1% to 10%) in conventional PCR and 0.05 to 5.0 ng (0.1% to 10%) in real-time PCR. A small-scale test with food samples showed promising results, with species identification possible even in heavily processed food items. Overall, this study presents a rapid, specific, and sensitive method for salmon species identification that can be applied to mixed-species and heavily processed samples in either conventional or real-time PCR formats. Practical Application: This study provides a newly developed method for salmon and trout species identification that will assist both industry and regulatory agencies in the detection and prevention of species substitution. This multiplex PCR method allows for rapid, high-throughput species identification even in heavily processed and mixed-species samples. An inter-laboratory study is currently being carried out to assess the ability of this method to identify species in a variety of commercial salmon and trout products.