Academic journal article The American Biology Teacher

Using Phylogenetic Analysis to Detect Market Substitution of Atlantic Salmon for Pacific Salmon: An Introductory Biology Laboratory Experiment

Academic journal article The American Biology Teacher

Using Phylogenetic Analysis to Detect Market Substitution of Atlantic Salmon for Pacific Salmon: An Introductory Biology Laboratory Experiment

Article excerpt

In the introductory biology curriculum, molecular and cellular biology present a unique challenge; the technology in these fields is advancing so quickly that the laboratory experience often lags behind the lecture material. As a result, many instructors struggle to maintain a compelling connection between lecture information and laboratory exercises. There is a tendency to emphasize basic techniques over concepts (the gel electrophoresis lab, the PCR lab) or to (re-)confirm widely known information (such as visualizing DNA in cells) rather than place the emphasis on true inquiry, modeling the process of the scientific method. A recent "call to action" by the American Association for the Advancement of Science (AAAS, 2011) emphasizes the importance of inquiry-based exercises at the introductory level as one of the top priorities for engaging students in science. As Alberts (2009) argued, we must engage students in authentic scientific inquiry from the very beginning of their college experience (if not earlier).

Student engagement can also be enhanced by taking inquiry outside the classroom and connecting students to their local neighborhood, community, or broader regional issues. Projects that stimulate students to consider the broader societal context and address questions that have real-world implications can transform the student experience because they are not just learning about science, they are actually doing science, and thereby becoming part of the scientific community. In our experience, projects that connect students to their local community engage them at a much more visceral level.

We developed this laboratory exercise to allow students to apply DNA sequencing and phylogenetic analysis to the socially relevant goal of detecting market substitution of Atlantic salmon, which is mostly farmed, for Pacific salmon, which is mostly wild-caught. Pacific salmon include six closely related species within the genus Oncorhynchus: chum (Oncorhynchus keta), coho (O. kisutch), chinook (O. tshawytscha), pink (O. gorbuscha), sockeye (O. nerka), and Japanese cherry (O. masou). Of the Pacific salmon, only coho and chinook are farmed, and only on a limited scale, whereas >90% of farmed salmon are Atlantic salmon (Salmo salar; see http://www.fao.org/fishery/culturedspecies/Salmo_salar).

Market substitution of seafood is surprisingly common; for example, using DNA sequence analysis, Wong and Hanner (2008) found that 25% of seafood samples marketed in the United States were potentially mislabeled. A high school independent project used similar methods to detect market substitution in 23% of seafood samples from Manhattan restaurants and stores (Stoeckle & Strauss, 2008). A Bellingham, Washington, fish processor was recently sentenced to prison and a substantial fine for substituting >160,000 lbs of coho for king salmon over a 2-year period (Durkan, 2011), but this is the exception; in most cases, market substitution is undetected and unpunished. Market substitution can be harmful to society on multiple levels: (1) financial losses of consumers paying too much for the product (consumer fraud), (2) reduced purchases of environmentally sustainable wild salmon in favor of environmentally damaging farmed salmon, and (3) undermining of consumer confidence in the accuracy of eco-labeling (Jacquet & Pauly, 2008).

Farmed salmon negatively affect the environment through nitrogen and phosphorus contamination from feed and fish waste (Wu, 1995). Farmed salmon have up to 10x higher concentrations of fat-soluble organic pollutants such as dioxins, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) (Hites et al., 2004a, b; Hamilton et al., 2005; Hayward et al., 2007). Salmon farms can have detrimental effects on native salmon populations by spreading parasites and diseases (McVicar, 1997), and escaped Atlantic salmon can interbreed with Pacific salmon, and compete directly with native fish for space and food (Gross, 1998). …

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