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By Rabbi Dovid Cohen, Administrative Rabbinic Coordinator
Q. When it comes to fish, such as salmon, does it need to be purchased at a kosher supermarket or can I buy it at a general supermarket?
A. There are two issues to consider when purchasing raw, fresh fish.
Firstly, one must be sure the fish is, in fact, a kosher species. As a rule, one may not rely on the name of the fish to make that determination as (a) in some cases multiple fish are referred to by the same name and (b) there is considerable fraud in the fish industry with one fish being passed off as another. Therefore, the only reliable method of determining that a fish is from a kosher species is by inspecting its scales to be sure that they are the type that can be removed from the fish without ripping any flesh. [This is an easy skill to learn: just give yourself a few minutes of practice with a piece of kosher fish that has scales on it]. If the fish has no scales, there is no way to know that the fish is from a kosher species. One notable exception is salmon, where the flesh-color is unique and is considered a clear identifying mark of the kosher, salmon fish.
Secondly, the knives used to scale, eviscerate, fillet and/or cut the fish may have been previously used for non-kosher fish. If that were true, it is possible that some residue of the non-kosher fish is still on the knife and will transfer to the kosher fish. To avoid this issue, it would be best to purchase cut fish from a kosher fish store, or at least to ask the store employees to clean the knife and work on a clean piece of butcher-paper. If neither of those are possible, there is basis to permit the purchase of packaged, pre-cut fish with the assumption that the store employees used the knife to cut many slices from the same kosher fish, and the non-kosher residue is likely not on the piece you chose. The worst-case scenario would be if the store would use a dirty knife to cut just one piece of kosher fish for you; in that case, you would have to scrub clean any surfaces that had been cut.
Of course, the above only applies to raw fish; fish which is cooked, smoked or otherwise processed requires proper kosher certification. What about if the salmon is raw but it has spices, color, or other additives? The simple answer is that the additives will need to be judged to determine if they are kosher-sensitive. For example, if all that was added was salt and pepper, then you can buy the salmon without concern, but if flavor or an unidentified “seasoning blend” was added, then you should only buy it with hashgachah. The addition of “color” adds an unexpected wrinkle. There is a red/orange color made from insects (known as carmine) which is not kosher, and the possibility that this was added would warrant caution. But when a package of salmon says “color added” it refers to something else. Namely, salmon are (relatively) unique in that they store certain carotenoids in their flesh, which is what provides their flesh with its distinct pinkish color. Wild salmon ingest these carotenoids as part of their regular diet, but farmed salmon, which grow in a controlled environment where those carotenoids are not naturally available, must have astaxanthin or canthaxanthin added to their feed, so that they will develop the proper color. Although these items are added to the feed and not to the fish’s flesh, the American law requires that salmon fed these items be labeled as having “color added”. Such feed does not pose a kashrus issue, because the materials are inherently kosher, and because they are digested by the fish. Thus, “color added” to salmon does not pose a kashrus concern.