Educated kosher consumers are well aware that kosher fish require two characteristics, fins and scales. However, many are uninformed about the relevance of insects to the kashrus of fish. Despite a familiarity amongst consumers about tolayim issues in fruits and vegetables, many are unaware of discussions in Shas and Shulchan Aruch about how this area pertains to the fish industry.
The gemara in Chullin (67b) states that insects, referred to as “darna”, found in the bellies of fish are prohibited and those found in the flesh of fish are permitted. The distinction between insects found in the stomachs or flesh of fish, lies in their origin. The gemara and rishonim explain that insects found in stomachs are presumed to be swallowed by the fish, while those found inside the flesh are grown inside the fish itself. Mature insects swallowed by fish are considered sheratzei hayam and are prohibited, while insects grown inside the flesh are not considered sheratzei hayam and are permitted until they exit the fish into the ocean. Although the Rambam (Hilchos Ma’achalos Assuros 2:17) makes a distinction between insects grown inside flesh while they fish is alive and while it is not, the position of all other rishonim is that insects grown inside the flesh of fish are permitted even when the fish is alive. The Shulchan Aruch Yoreh Deah (84:16) rules clearly that all insects found in the bellies of fish are prohibited, while those found in the flesh are permitted.
This issue has gained considerable attention recently due to claims by marine biologists that insects found in the flesh of fish are not generated inside the fish itself. Scientists have been contending that insects found in the flesh of fish, like salmon and whitefish, are initially swallowed by other smaller fish that are a food source of larger fish. The insects eaten by the smaller fish subsequently penetrate the larger fish and become lodged in their flesh. Based upon these facts and the basic halachic guidelines above, it would appear these insects should be prohibited. However, these contentions seem to contradict the Shulchan Aruch, which permits insects found in the flesh of fish without restriction.
A general discussion of how to approach scientific claims that are contrary to Chazal is beyond the scope of this article. This particular question has been discussed by Gedolei Yisroel during the past several decades, although there is very little written about it. Rav Shmuel Vosner wrote a teshuva (see Shevet HaLevi 4:83) about this subject, and grappled with the apparent discrepancy between Chazal and scientific contentions. Rav Vosner speculates that perhaps the gemara’s mention of “darna” is referring to a specific type of insect. However, since nowadays we can not distinguish which insects are considered “darna” we should assume that they are all prohibited, even when found in the flesh of fish. Nevertheless, Rav Vosner acknowledges that the Tur and Shulchan Aruch do not distinguish between different types of insects. According to the Tur and Shulchan Aruch all insects found in the flesh of fish are permitted, without restriction. Rav Vosner is somewhat inconclusive in this teshuva, although subsequently wrote a more definitive position suggesting that people should be vigilant in this area (see Shevet HaLevi 7:127:3). Moreover, in 1997 Rav Yosef Shalom Elyashiv shlita took a stringent position in this area regarding whitefish. Rav Elyashiv is quoted as accepting the testimony of marine biologists, but limited only to very specific instances when scientific evidence supports that the insects entered the fish from the ocean. This would not be considered a contradiction to Chazal, since Chazal never stated that it is impossible for insects from the ocean to become lodged in the flesh of fish (see Bedikas HaMazon KeHalacha Volume I, pp. 112).
Rav Moshe Feinstein zt”l has often been quoted as being lenient on this matter. Although assuming these insects originated from outside the fish is not necessarily a direct contradiction to chazal, it does not immediately render the insects prohibited either. Insects found in the flesh of fish are very small. Presumably, the insects are not noticeable to the naked eye until they mature inside the fish itself. Chazal in their infinite wisdom have declared “lo nitna Torah LeMalachei HaShares” (“the Torah was not given to angels”. See Berachos 25b). As a general rule, insects that are noticeable only through extraordinary means are not prohibited. In essence, these insects would still not be considered prohibited until they exit the fish into the ocean. It is said that when Rav Moshe zt”l was initially approached to write a teshuva about this topic he respectfully declined, explaining that the answer is clearly found in the Shulchan Aruch.
When approaching this issue it is important to bear in mind two considerations. First, recent scientific contentions about the physiology of fish need not be accepted to the exclusion of Chazal. Rav Vosner suggests in his teshuva the possibility that both are correct and halacha allows us to assume that the origin of insects found in the flesh of fish are not from outside the fish, but grown inside the fish itself. Moreover, there is a basic fundamental difference between science and Torah. The field of science is forever changing and developing, while a critical foundation of our emunah is that Torah is eternal and constant. Scientific and medical theories of yesteryear, often taken for granted, have proven fallacious and outdated over time. This trend has continued throughout history, as medical and scientific developments continue contribute new theories, while previous scientific beliefs become obsolete.
Many Gedolei Yisroel, both in Eretz Yisroel and the United States, regarding this particular issue took the position that current scientific evidence can not be accepted in a manner that seemingly contradicts Chazal, with a general line of reasoning similar to Rav Moshe zt”l. The list of Gedolei Yisroel that have been lenient with this matter in addition to Rav Moshe Feinstein zt”l include, Rav Shlomo Zalman Auerbach zt”l, Dayan Yitzchok Yaacov Weiss zt”l, Dayan Yisroel Yaacov Fisher zt”l, The Klausenberger Rebbe zt”l, and Rav Abba Shaul zt”l, amongst others (see Bedikas HaMazon KeHalacha Volume I, pp. 112).
The position of most kashrus agencies internationally about this topic has been lenient, consistent with the simple reading of the Shulchan Aruch. Although there are poskim who suggest that one should be vigilant in this area, the general consensus amongst most Gedolei Yisroel has been to continue accepting the position espoused in the Shulchan Aruch, and followed by previous generations.