An Analysis of Kaskeses Part 2

An Analysis of Kaskeses – past and present Rabbi C. Goldberg HaModia, May 17, 2006

In part one of this article, which appeared in the March 22nd edition of HaModia, we discussed what the requirements are for fish to be kosher (i.e. that the fish needs to have “kaskeses” and what is a “kaskeses”), as well as some of the common mistakes made in trying to determine which fish would qualify as kosher. In this article, we will discuss two practical methods to determine if a fish is kosher.

The easiest way to determine if a fish is kosher, is by manually checking the fish for scales[1]. Simply locate a scale on the side of the fish (preferably behind the gills, tail or fin – as mentioned by the Rama as a chumra to guarantee the scale did not fall off of another fish), grab it between your thumb and forefinger, and gently attempt to pull it out. One should note that scales are always attached to the fish on the side closer to the head. The reason is fairly obvious if you can imagine how a fish swims. If the scale would be attached to the skin at the side closest to the tail, the current would pull the scale away from the skin and would inevitably rip it off as the fish swims. Imagine an open umbrella in a brisk wind that is not pointed in the direction of the blowing wind. The umbrella would get caught in the wind and blow inside out. So too, the current would get caught under an inverted scale and rip it off, causing the fish to die due to infection.

After removing the scale, simply inspect the area where the scale came from and check if there is a rip in the skin. If the skin seems fairly undamaged, the fish is kosher. If the scale will not come out without the skin ripping, the scale is not a “kaskeses”. Generally speaking, it is fairly obvious if the skin ripped. As a practical way to get a sense of what skin normally looks like when a “kaskeses” is removed (and the skin does not rip) one could inspect the scaleless skin of fish which one knows to be kosher.

As long as a fish has “kaskeses” at some point in it’s lifecycle it is permitted and there is no requirement of “mesorah” (i.e. a tradition that identifies a particular fish as a kosher species). Fish that lose their scales often have a single scale in the three areas mentioned earlier (behind the gills, tail and fin), though even without a scale present one could still recognize a kosher species of fish based on its skin. The Darchei Teshuva describes the possibility of determining the kosher status of a scaleless fish based on “mesorah”. The “mesorah method” is derived from an idea mentioned in our previous article article, namely that the Gemara tells us that a fish that has not yet grown “kaskeses” or lost its “kaskeskes” is still a kosher specie. One should ask, even if theoretically true, how could one practically determine that the fish is kosher if there are no “kaskeses” on it now? The answer, says the Darchei Teshuva, is that one can recognize the specie based on its skin. There is no mention of someone with a “tvias ayin” on the flesh of a fish, which must be regarded as “kirvei dagim”[2] and is forbidden.

Therefore, one may bring a fish whose “kaskeses” fell off or did not yet grow “kaskeses” but whose skin is still attached to someone familiar with the specific fish to determine if this is a species that is subject to a mesorah of being a kosher fish. This “mesorah method” of determining kosher status is particularly useful when dealing with various types of mackerel. Mackerels tend to lose their scales when removed from the water, and the mesorah method can be used to permit the scaleless mackerel. Generally, this mesorah method does not apply to fish whose skin is removed.[3]

It is essential to note that the person ruling on the fish must be both “halachicly” reliable and familiar with the issue at hand (in our case, the specific type of fish). A typical worker at a fish store is not qualified to confirm the kosher status of the fish.[4]


Some have asked how big a piece of skin must be left on the fish for one to determine its status based on the “mesorah method”. Though I have not seen a specific size given, clearly the piece of skin must be big enough for someone to actually be able to say what species it is. A few weeks ago, I received an inquiry from a small hashgacha organization, that wanted to know how they could accept as kosher fish whose skin had been completely removed except for a small (scaleless) patch, when their mashgiach could not properly identify the fish. I answered that they could not. The only way to accept the fish is by having someone familiar with the specie accept the delivery, and a mashgiach who is not familiar with the specific fish is not qualified to accept such fish. Consider the following mashal (parable). Suppose a person, r”l, is blind. Halachicly, the person is “ne’eman” to testify in Beis Din. One would not, however, ask the person to confirm which of two identical pieces of meat has a hashgacha printed on the package. Here too, a person who does not have mesorah on the particular fish in question may not be relied upon to confirm the kosher status of the fish by a patch of skin. Such a person could only attempt to remove a scale from the fish, as described above.

Some hashgacha organizations allow for salmon to be accepted without skin at all. The justification behind this policy is that there are no known fish whose flesh resembles the red/pink of a salmon, making the flesh color a “siman muvhak” (an absolute indentifier of the fish, which would pre-empt the requirement of checking for scales). Again, this heter would only apply to a case where the mashgiach accepting the fish knows what a salmon is supposed to look like.

Many of us are “zoche” to live in areas where we don’t much think about which fish are kosher or not, as we could not imagine the local “heimish” supermarket selling a non-kosher species. Some of us live in parts of the world where kosher meat is difficult to acquire, and buying fish from the local store is the easiest way to properly feed our families. Though it may seem odd at first, people living neighborhoods which do not have kosher fish stores have at least one advantage over their brethren living in neighborhoods that do. They have the chance to teach themselves and their children how to determine if a fish is kosher, often having no other option. It would be unfortunate if those of us who can easily acquire a kosher fish would lose out on the opportunity to know how to be “mavchin bein hatamei u’bein hatahor”, to be able to distinguish between the pure and the impure.

Rabbi Goldberg has been working as a Rabbinic Coordinator in the Orthodox Union for four years, specializing in kosher fish. He has spoken at various school groups and professional conferences. If you would like to arrange for him to make a free kosher fish demonstration for your shul,school or learning group anywhere in the US or Canada, please feel free to contact the Orthodox Union at 212-613-8340.

[1] As discussed in the first part of this column, from the March 22 edition, there is no practical requirement of checking for fins.
[2] See Y.D. 83:7. This is the term given to skinless fish innards, which aren’t kosher unless prepared under hashgachah.
[3] Some species, however, can be identified as kosher even after the skin is removed. A common example of such fish is salmon.
[4] The rules of “mirsas” and “aman lo mareh umnaso” likely do not apply in the typical consumer situation, where the persons serving the consumer have neither fear of making a mistake, nor negative ramifications by implying that a specific fish is kosher. The FDA (see FDA Consumer Magazine September 1993) also recognizes the prevalence of misidentification of species in the fish industry. Therefore, one should not readily rely on a storekeeper to identify the species of fish.