There are many reasons you would want to know just exactly what you are paying for. If you are monitoring your diet closely, you might want to know in detail the type of food that you are putting into your body. This is especially important for individuals who regularly consume fish as different species living in different environment could contain drastically different macro and micronutrients. Moreover, the concentration of pollutants such as mercury and microplastics also varies depending on their position in the food chain [1, 2].
Another reason is financially related. Imagine paying for the more expensive persimmons only to be getting tomatoes, how would you feel? Likewise, nobody likes to be swindled into purchasing products that they have never intended to buy or much worse, getting substitutes with inferior quality.
Unless you are a vegetarian, there is a good chance that you have eaten fish before. But just exactly how well do you recognize them when they're still alive and swimming? Before we explore today's topic further, take a closer look at the three fishes below. If you have lived or at least eaten fish in Southeast Asia, you would have at least came across a type of fish known as the "Dory" before. Which of the following "Dory" fish did you expect to be served to you in a restaurant or sold to you in a fish market and which one did you actually get?
[3, 4, 5]
While salmons and trouts are highly recognizable from their pinkish-orange flesh, skinless white fish fillets are virtually indistinguishable. In Malaysia, a kilogram (~2.2lbs) of wild halibut can cost upwards of RM50 (~$12.50) whereas a kilogram of farmed raised tilapia may only cost around RM15, a price difference of more than threefold for fish fillets of the same weight. Therefore, it is not uncommon for merchants such as fish dealers and restaurants to masquerade cheaper seafood products into more expensive one to maximize profit, a worldwide practice known as the seafood fraud . According to this study that utilized DNA barcoding to sample 62 seafood products in Malaysia, 16% of them were found to be mislabeled. Probabilistic speaking, one out of six seafood product in your fridge right now is not what it claims it to be. Yikes.
A sandfish? Is that even a part of a piscivorous diet?
You see, the same animal can be called many names. In different parts of the world, a crayfish can also be known as a crawdad, a mini lobster, a yabby, and even a mudbug. A common name such as "Dory" can change or evolve into something else depending on media influences, cultural references, and geographical location. This also means that it can be misleading depending on the context that it is being used in, as illustrated by the fish identification question above. To add to this whole confusion, take a look at more of these fishy examples below:
If you haven't already noticed, non of these are actually true fish! The crayfish is a crustacean, the jellyfish is a cnidarian, the starfish is an echinoderm, the cuttlefish is a mollusc, and the sandfish is actually a reptile! Isn't that just too confusing?
How does binomial nomenclature in taxonomy fit into today's discussion?
Fortunately, there is a way to go about that. In taxonomy, the usage of a "two-terms" system known as the binomial nomenclature universally standardizes how an organism is being named to prevent misidentification. Whether you are from China, the United States or Malaysia, scientific names (that are always written in Latin) help everybody to identify and recognize the same species regardless of language and cultural differences.
In general, there are two modern approaches to identify species - molecular systematics (a.k.a DNA barcoding which involves sequencing a short strand of genetic material from an unknown specimen to compare with that of a known species) and morphological systematics (identification based on comparing the anatomical characteristics and forms between different animal groups). Molecular systematics often require highly specialized tools to perform, whereas morphological systematics can usually be conducted via examining the internal parts (e.g., bone structure, presence/absence of specific organs and their relative placement) and external features (e.g., body form and other physical characteristics) of carcasses given some forms of understanding in basic anatomy.
I am not saying that everyone needs to master binomial nomenclature and morphological systematics. But simply knowing that they exist, willing to invest some time and efforts into learning them, researching and comparing food labels (using species' binomial name) with the actual products, as well as staying away from products that aren't labeled properly would certainly help to reduce the likelihood if not altogether preventing anyone from being the next victim of seafood fraud. While many seafood products still require advanced DNA testing to be correctly identified, consumers equipped with some knowledge in taxonomy and morphological taxonomy (e.g., knowing that all catfish has barbels , sharks have unique placoid scales which give their skins a sandpaper like texture ) will certainly be less likely fooled into purchasing inferior substitutes should tangible, whole or recognizable seafood parts are presented.
A - Pacific Blue Tang (Paracanthurus hepatus)
A type of surgeonfish. Mostly inedible and is usually kept as an ornamental fish.
B - John Dory (Zeus faber)
A type of edible marine fish.
C - Iridescent shark / Pangasius catfish (Pangasius sp.) A type of edible freshwater catfish. Sometimes kept as an ornamental fish. Fun fact: In Canada, the United States, and Australia, the Pangasius catfish is more commonly called a "swai" or a "basa". Many people (including Malaysians) do not realize that this is in fact a type of catfish.
> Locally, the freshwater Pangasius catfish is often sold as the more expensive, saltwater John Dory.
References:  https://pubmed.ncbi.nlm.nih.gov/25486051/