Halakhah su Levitico 10:10

The presence of snapir ve-kaskeset, usually translated as "fins and scales," is the distinguishing criterion which serves to identify those species of fish which are permitted as kosher. The term "scales," however, is an inexact translation of the biblical term kaskeset which occurs in Leviticus 11:9. There exist a variety of anatomical structures known as "scales" which do not satisfy the halakhic definition of kaskeset. As evidenced by the terminology employed by the Gemara, Avodah Zarah 39a, and by Targum Onkelos, Leviticus 11:9, the term kaskeset denotes only scales which can be "peeled" or removed without injury to the underlying skin.¹See also Ramban, Commentary on the Bible, Leviticus 10:10; Tiferet Yisra’el, Ḥullin 3:96; and R. Menachem Mendel Schneerson, Teshuvot Ẓemaḥ Ẓedek, Yoreh De‘ah, no. 61. Cf., Teshuvot Noda bi-Yehudah, Mahadura Tinyana, Yoreh De‘ah, nos. 28-30, and Teshuvot Ketav Sofer, Yoreh De‘ah, no. 45. In terms of biological classification, both ctenoid scales and cosmoid scales possess this characteristic. Scales of other types, are, in fact, projections or tubercles of the skin itself rather than a separate covering. Since scales of non-kosher species are integral to the skin itself, removal of such scales causes damage to the skin. Such damage can be observed visually at the time of removal. Thus, whether or not the scales of a particular species meet the criteria of kaskeset may be established at the time of their removal. Removal of the scales without damage to the skin establishes that the scales removed constitute a separate covering, or kaskeset, and not merely projections of the skin itself.²See Dr. Israel Meir Levinger, Mazon Kasher min ha-Ḥai, 2nd edition (Jerusalem, 5740), pp. 92 ff.