A Fishy Tale (and Scale)

In this week’s parsha, the Torah teaches that every fish that has fins and scales is kosher. The Mishnah (Niddah 51b) notes that all species of fish with scales also have fins. Thus, one may assume that a slice of a fish with scales is kosher even if one sees no fins.

The Gemara (Chullin 66a) states further that a fish species that has scales at any time during its life is kosher. Therefore, a fish is kosher even if “it has no scales now, but they will grow later, or it has scales and they fall off when the fish leaves the water.” Thus, sardines are kosher even though sometimes they are caught before scales develop. Similarly, certain herrings that shed their scales upon harvest are also kosher.

The early Acharonim discuss a variety of fish, or more accurately some type of legged sea creature, called the Stincus marinus that inhabited the seas near Spain and was reputed to have scales but no fins. The Tosafos Yom Tov, in his commentary to the Rosh (Chullin 3:67, Maadanei Yom Tov #5) records that when he was a rav in Vienna he was shown a specimen of this fish, which is naturally toxic, but the toxins can be removed and it can (and was) used for food and medicine. Maadanei Yom Tov presents a few possible explanations why this creature does not defy the rule established by the Gemara.

Some poskim ruled that this creature is unquestionably non-kosher, and that the Gemara means that there are very few sea creatures that have scales and no fins. One may assume that a fish or other sea creature one finds with scales is kosher; however, if one knows that it has no fins it is non-kosher (Kereisi 83:3; HaKsav ViHakabalah, Vayikra 11:9). Other poskim contend that the Gemara’s rule is inviolate and without exception (Pri Chodosh YD 83:4). In their opinion, Stincus marinus must have fins, but they fall off in the sea or when they are young; and it is indeed kosher.

What is very curious is that according to our contemporary scientific data, the creature that the Maadanei Yom Tov was referring to is probably a type of lizard and not really a sea creature at all.

To summarize, one may assume that any fish one discovers with scales is kosher, and it suffices to check an unknown fish for scales in order to verify that it is indeed kosher (Shulchan Aruch, Yoreh Deah 83:3).

The word used by the Torah for scales, kaskeses, refers to a scale that is removable from the skin (Rama, Yoreh Deah 83:1). Thus, fish like sturgeon whose scales cannot be removed from the skin are not kosher (cf. Noda BiYehudah).


I live in a town without a kosher fish market. May I purchase fish fillet from a species that I know is kosher?

Halachically, one may only use skinned fish that was supervised from the removal of its skin until it was sealed as kosher (Gemara Avodah Zarah 39b). Once the skin has been removed, one may not use it without proper seals because of concern that the fish is not the kosher species one thinks it is, but a similar looking non-kosher fish.

What if a non-Jew or a non-observant Jew guarantees that this is a kosher fish?

The halacha is that one may not rely on the non-Jew and the product must be sealed by an observant Jew (Gemara Avodah Zarah 39b). However, there is one instance where we may rely on a non-Jew’s testimony – when he knows that he will lose financially if he is caught deceiving us (Taz, Yoreh Deah 83:9). Therefore, if the non-Jew knows that we can independently verify his information, we may rely on him.

However, one is usually unable to verify the information provided by the person behind the counter in a non-kosher fish market. Therefore, since he is unafraid that we will catch him lying, one may not rely on his authority.

The poskim of a generation ago disputed whether one may purchase fish without skin from a non-Jewish company that has business reasons to produce only a certain type of fish that is kosher. May one use fish from a plant without having a mashgiach check every fish? This question affects production of canned tuna or salmon. Does it require a round-the-clock mashgiach checking that every fish is kosher, or can we rely on the fact that the company has its own reasons to pack only the type of fish stated on the label?

Some poskim hold that one may rely on the company’s business reasons because of the halachic principle, “uman lo marei umnaso,” a professional does not damage his reputation. According to this approach, we may assume that a company would not mix a different, non-kosher species into its canning operation because it is detrimental to itself (Rav Aharon Kotler; Shu”t Chelkas Yaakov 3:10). Other poskim contend that Chazal did not permit this lenience in the production of kosher fish but require full-time supervision under all circumstances (Shu”t Igros Moshe, Yoreh Deah 3:8; Kisvei Rav Henkin, 2:53). Many of the major hechsherim in the United States follow the lenient opinion.


According to the lenient opinions cited, could one allow a company to produce whitefish salad without a mashgiach? After all, whitefish is a kosher fish.

This is disputed by contemporary poskim. Some contend that this is prohibited according to all opinions of the earlier generation, since the company can mix small amounts of less expensive non-kosher fish into the whitefish salad without it being discerned. Thus, the company’s professional reputation is not at stake. Other poskim maintain that it suffices to spot-check that no non-kosher fish is in the factory since the company’s professional reputation is at stake.


How can someone purchase fresh fish if he lives in an area that does not yet have a kosher fish market? Since he may not rely on the fishmonger’s assurances, must he forgo purchasing of fresh fish?

There is a perfectly acceptable halachic solution. Once should go to the fish store, identify a fish that still has its skin on and identify the scales. One should then provide the store with one’s own knife and supervise the fish’s filleting.


The fish store knives usually have a thin layer of grease from other, possibly non-kosher, fish (see Shulchan Aruch, Yoreh Deah 96:5). One cannot assume that the store cleans the knife between fish to the extent halacha requires to guarantee that it is totally clean (ibid.).

In the rare instance that the shop is reticent to allow the use of private knives, then you should supervise that the knives are scraped extremely clean. Standard cleaning does not guarantee that the grease has been removed from the knife.


Salmon is a very healthy fish, high in omega oils. It is also a kosher species.

Many years ago, I attended a conference of rabbonim where a highly respected posek stated that one may assume that salmon fillet is always kosher, even without its skin. He explained that salmon meat’s red or pink color does not exist in any non-kosher fish species. Therefore, he contended that one may safely assume that red or pink colored fish is kosher (Shu”t Igros Moshe, Yoreh Deah 3:8).

I did some research on this subject. There is a basis to this statement, but it is not as simple as had been presented at the time. Indeed, there are several non-kosher fish, including some varieties of shark and catfish, that have a pink pigment. However, there are distinct shades of red and reddish pink that belong only to salmon and to certain varieties of trout that are also kosher. One should not rely on determining that a certain fish is kosher based on its hue without training.

Although this halacha was presumably true at that time, I am uncertain whether one may still make this presumption because of an unusual snippet of news I discovered.

I recently read an article comparing the environmental benefits of commercially sold Pacific salmon to those of Atlantic salmon. Pacific salmon are wild fish that roam the oceans and pick up their red or pink color from their natural diet that includes red crustaceans. (The fact that a fish consumes non-kosher creatures does not affect its kashrus.) However, commercially sold Atlantic salmon, the source for fillets and steaks, are bred in fish farms that populate the coasts of the Atlantic Ocean and its inlets. (Atlantic salmon is no longer harvested directly from the sea because of decreasing wild populations.) These fish eat a diet that does not make their flesh pink. To give the fish their trademark hue, the farmers add colorant to their diet.

It seems that any fish wandering into these farms and sharing the salmons’ diet would also develop pink flesh, which would destroy the theory that every pink fish must be kosher. Indeed the fish could be non-kosher but have devoured significant amounts of red color.

After further research, I discovered another reason why salmon and trout have a distinctive color not found among other deep sea fishes. When most sea creatures eat colored crustaceans, they store the excess pigment in their skin. Only salmon and trout store the color in their flesh. Thus, many respected rabbonim still maintain that fish with the distinctive salmon color must be kosher since only salmon and trout are able to convert their food coloring to their flesh.

However, a research scientist I spoke to dismissed this argument for two reasons: First, he pointed out that it is virtually impossible to prove that no other fish has this ability. To do this, one would have to conduct research on every fish variety worldwide which is an impossible task. Furthermore, he pointed out that the ability to transfer food color to flesh is an inherited characteristic that the salmon possesses in its DNA. It is feasible that someone has isolated this gene, and that some fish farmer is marketing a different species of fish as salmon fillet. Thus, our question whether one may assume that all red or pink fillet is kosher remains valid.

Nonetheless, I personally side with the lenient ruling. Since we have no evidence of a non-kosher, reddish-flesh fish, I think that we may still assume that any fish with this distinctive color is salmon until evidence appears that someone has isolated the gene that allows the color to be stored in the flesh and transferred it to a non-kosher species. Until we have such evidence, if the fish looks like salmon and smells like salmon we will assume that it is salmon (see Shach, Yoreh Deah 83:27).


Are there any other potential kashrus issues with canned fish?

Fish factories often produce non-kosher products that would render the tuna or salmon non-kosher. Additionally, even if the factory only cans kosher fish, it might use non-kosher ingredients. Most fish is processed in oil, which can be non-kosher or be produced on non-kosher equipment.

There is also a discussion among contemporary poskim whether canned tuna or salmon is prohibited because of bishul akum, food cooked by a non-Jew. Explaining this complicated subject will be left for a different article.

What other halachos pertain to fish?


Chazal advise that consuming fish and meat together is harmful to one’s health (Gemara Pesachim 76a). To avoid swallowing fish and meat together, one should eat and drink something between eating fish and meat in order to clean the mouth from residual particles (Rama to Yoreh Deah 116:3). Sefardim are more stringent and follow the ruling of the Shulchan Aruch who rules that one must wash one’s hands and mouth carefully between eating fish and meat (Shulchan Aruch, Yoreh Deah 116:3).


I have never noticed anyone getting sick from eating fish and meat together. Furthermore, the American Medical Association does not consider this harmful. Does this affect halacha in any way?

Some prominent poskim contend that although mixing fish and meat was unhealthy in the days of Chazal, today the nature of the world has changed and it is no longer unhealthy (Magen Avraham 173:1). This concept is referred to as “nishtaneh hateva,” that nature has altered since the days of Chazal (see Tosafos, Moed Katan 11a; Gemara Niddah 3a). Others contend that Chazal were concerned only about a specific type of fish that is dangerous to mix with meat, and that their concern does not extend to other varieties (Shu”t Chasam Sofer, Yoreh Deah #101).

Other poskim rule that one should still not eat fish and meat together since Chazal may have been aware of a medical issue unknown to modern medicine (see Shu”t Shvus Yaakov 3:70; Shu”t Chasam Sofer, Yoreh Deah #101). The accepted practice is to be stringent (Shulchan Aruch, Yoreh Deah 116:3).


Chassidim have a minhag to drink schnapps after fish. Does this practice have a halachic source?

Indeed it does. Some poskim cite that it is dangerous to drink water immediately after fish (Tosafos, Moed Katan 11a; quoted by Aruch Hashulchan, Yoreh Deah 116:10; another source one could possibly quote for this minhag is a Shla, quoted in Darkei Teshuvah 116:31, who implies that one should drink a beverage after fish, but not water). In earlier generations, there were not too many beverages available; often water, wine, and schnapps were the only choices. Thus, when wine was expensive, and one did not want to drink water after fish, schnapps was the most practical alternative. I suspect that this is the origin of washing down fish with schnapps (see Shaar HaTziyun 174:46). Today, a wine connoisseur can substitute white wine and a teetotaler, juice, for the same purpose. (Someone asked me whether one can use soda or reconstituted juice for this purpose, since both are predominantly water. To this date, I have found no halachic discussion about this shaylah.)


Question: My bubbie had a special pot that she used only to cook fish. Is there halachic significance to this fish pot?

Although most poskim contend that there is no halachic or safety problem with cooking fish in a fleishig pot, some poskim are stringent (Taz, Yoreh Deah 95:3; Shu”t Shvus Yaakov 3:70). Based on this concern, many people have a family custom to cook fish only in a pot that they never use for meat. However, the common practice is to allow the cooking of fish in meat pots.


Based on certain halachic sources, some people, most commonly Sefardim, have the practice not to mix fish and milk products together (Pischei Tshuvah, Yoreh Deah 87:9). This is important for an Ashkenazi to know when he invites Sefardi guests for a milchig meal.


People often ask the following question: Some steak sauces or Worcestershire sauces have anchovies or other fish products among their ingredients. I have noticed that some hechsherim place a notation next to their hechsher symbol identifying that these items contain fish, whereas sometimes they do not. Is this an oversight?

The answer to this question requires an introduction. Poskim dispute whether any admixture of fish and meat is dangerous or whether it is dangerous only if there is enough fish and meat to taste both (see Taz Yoreh Deah 116:2; Pischei Tshuvah 116:3; Darchei Tshuvah 116:21). Thus, many poskim permit eating a small amount of fish mixed into a meat product. For this reason, and because of the above-mentioned opinion of the Magen Avraham that mixed fish and meat is no longer dangerous since nature has changed, many poskim allow eating a small amount of fish mixed into a meat dish (Shu”t Chasam Sofer, Yoreh Deah #101; Pischei Tshuvah 116:3). Upon this basis, some hechsherim do not require listing fish in the hechsher when it constitutes less than a sixtieth of the product.

The Midrash (Breishis Rabbah 97:3) points out that Klal Yisroel is compared to fish. Just like fish, who are completely surrounded by water, rise excitedly to the surface at the first drops of rain to drink fresh water, so too Jews, although surrounded by Torah, run enthusiastically to hear a new chiddush of Torah, “drinking” it thirstily as if this was their first opportunity to learn. May we indeed live up to our reputation!