By Mordechai Kuber; Rav, Beis Medrash Nachlas Tzvi Ohel Avraham (Telzstone, Israel)

Synopsis: Shulchan Aruch permits fish flesh worms because they form in the permitted fish flesh, yet scientific research has discredited spontaneous generation.  For the past 150 years, many Poskim resolved this conflict by saying that these flesh worms appear to form in the flesh, but that they actually originate in microscopic form outside the fish, but develop to visible, halachically relevant form only within the flesh.  Scientists have now demonstrated that at least one common flesh worm, anisakis, is of visible size before ingestion, thereby refuting this approach.  Some conclude that these worms are therefore prohibited, but they ignore the impossible extrapolation of their reasoning that all flesh worms would therefore be prohibited, unless we are certain of any that are smaller than visible dimensions before they are ingested, and we are not.  They also ignore the opinions of Rishonim that worms are not migratory to fish flesh, and ignore both scientific and halachic evidence proving the same.  They present scientific opinions of migration, without recognizing that these positions are all predicated on, and fatally influenced by, a rejection of internal generation.  They also present anecdotal evidence of migration, which does not pass the rigor of scientific research and reporting. 
This article proposes that Halachah rejects migration to the flesh, even when identical intestinal worms are present.  Rather, we presume that flesh worms are internally generated, even if we are uncertain of the biological mechanism by which this occurs.  This approach simply resolves all difficulties but one – that scientists say that non-invasive worm generation is impossible.  In this matter, we reject the evidence of experimentation in favor of the word of Chazal, whose tradition-based biological knowledge exceeded human experimental abilities.

Background – Ferocious debate has erupted recently concerning contemporary worms found in the flesh of fish.  Shulchan Aruch (YD 84:16) explicitly rules that fish-flesh worms are permitted, because they originate within the flesh, whereas stomach worms are prohibited, because they enter the fish from the outside.  Many claim that Shulchan Aruch’s ruling is limited to ancient worms that did not migrate from fishes’ stomachs after they were ingested by the host fish.  This list of respected Poskim and Gedolei Hador base their ruling on scientific papers, and on evidence presented and interpreted by Rav Shneur Zalman Revach, an Israeli Rav with more piscatorial experience than many fishmongers, that indicate that contemporary fish-flesh worms migrate to the flesh from the stomachs. 

The Rabbanim who steadfastly cling to their position that even contemporary fish-flesh worms are permitted argue that Shulchan Aruch’s ruling is not limited to a specific type of worm.  Therefore, if the possibility exists that other worms, possessing migratory capabilities, are prohibited, the Shulchan Aruch’s blanket permissive ruling is unconscionably and irresponsibly misleading.  Rather, the blanket ruling proves that migration is impossible.  Therefore, the word of Chazal is pitted against the word of the scientists, and the Chazal’s word prevails. 

Most Poskim who prohibit contemporary fish-flesh worms acknowledge this difficulty, but some contest it.  HaRav Hagaon Rav Wosner Shlit”a entertains the possibility that some Rishonim, in contrast to Shulchan Aruch, do not interpret the Gemara as granting blanket approval to fish-flesh worms, but rather only to a specific worm.  Thus, even Talmudic law prohibits contemporary fish-flesh worms, for they are of a different species.  Rav Wosner acknowledges that Shulchan Aruch does not follow this view (Sheivet Haleivi 4:83 and 7:123). 

Rav Moshe Mordechai Karp, a distinguished neighborhood Rav in Kiryat Sefer who has championed this cause, suggests that many Rishonim and Poskim, and perhaps even Shulchan Aruch, do not issue a blanket ruling.  Rather, they permit flesh worms only if we are certain that they do not originate outside the fish.  However, they are prohibited if reasonable doubt exists concerning their origin.  Thus, migratory worms of yore that were comparable to contemporary worms, which are purportedly migratory, were prohibited even in Talmudic days, and the Talmud’s permissive ruling refers only to non-migratory worms, whose origin is certainly within the fish (Ohr Yisroel, Teves 5770). 

Poskim who prohibit contemporary fish-flesh worms, but unlike the aforementioned Poskim, acknowledge the difficulty presented by Shulchan Aruch’s all-inclusive permissive ruling, present two counter arguments.  First, Shulchan Aruch grants blanket approval only in the absence of contrary evidence.  Thus, Shulchan Aruch rules that one need not be concerned about the possibility that fish-flesh worms have migrated from the stomach, for such an occurrence is rare enough to permit ignoring its then infrequent, or non-existent, incidence.  But if we are faced with evidence that a certain worm has migratory powers, we cannot ignore it.  We are forced to say that this worm has developed, or enhanced, its migratory powers since the codifying of the Talmud and Shulchan Aruch.  Second, modern-day catching and delivery methods allow fish to remain ungutted for much longer than in centuries, or even in decades, gone by.  Therefore, although Shulchan Aruch rules that we may presume that freshly caught fish could not have migratory worms in its flesh, we cannot safely presume the same for fish caught days ago.  This latter argument is bolstered by Rav Revach’s purported demonstration of post-catch migration of stomach worms into adjacent flesh. 

The permitting Rabbanim argue that the force of tradition supports their position: since the codifying of the Talmud, no one has discussed today’s state of infestation where both the stomach and flesh are infested.  They posit that it is unreasonable to presume that such tandem infestation was never reached throughout the millennia.  Rather, there were certainly many incidences of such infestation, yet none of our sages of years gone by felt that the presence of nearby stomach worms negatively affected the permissibility of the flesh worms. 

The opposing camp dismisses this argument, and confidently proposes that this is an entirely new situation.  They postulate that continuing contamination of the waters and environment has created levels of infestation previously unknown.  They buttress their position by citing testimony of two fisheries that the level of flesh-worm infestation has risen dramatically over the last decades. 

On behalf of the permitting Rabbanim, we have an obligation to scrutinize the relevance and reliability of this miniscule fishery survey.  How many fisheries were contacted, and did they all agree?  Could the reported higher infestation levels result from more sophisticated detection methods?  Do we have any way of knowing, besides absolute conjecture, that today’s levels of infestation were never previously realized (see Koheles 7:10)?  Decades ago, when infestation levels were lower, were stomachs similarly infested in tandem with the flesh?  If yes, and so it seems from all available literature, this condition is not new at all! 

In summary, all agree that non-migratory fish-flesh worms are permitted, and that those that have migrated from the fish’s stomach are prohibited.  Most also seem to agree that in a head-to-head match, the word of Shulchan Aruch and Chazal discredits the word of dissenting scientists.  The only point of disagreement is whether the scope of this particular ruling of Shulchan Aruch is broad enough to directly contradict the claim that there are contemporary, migratory worms, whose incidence is frequent enough to require that fish flesh be inspected for their presence.  In addition, it behooves us to evaluate independently the integrity and legitimacy of the presented migratory evidence, even without invoking the against-Chazal disqualifier. 

There seems to be a peripheral issue, unrelated to the above discussion, of whether Gedolei Hador could be misled by misinformation, and whether a non-Gadol is entitled to challenge their halachic arguments.  A discussion of that issue is beyond the scope of this article.  For ease of presentation, this article presumes that Gedolei Hador would recant their position if they discovered that they had been misled, and that even non-Gedolim may debate an issue about which Gedolim have already issued their ruling.  Obviously, in the final analysis, we follow the rulings of our Poskim and Gedolim. 

Scientists and Halachah – Suggesting that nature has changed since the days of the Talmud is not novel; Magen Avraham (173:6) and Maharshal (Chulin 7:15) suggest the same.  However, granting credence to scientists as arbiters of post-Talmudic change is quite a departure from the halachic norm of old.  In theory, although the laws of our holy Torah do not bind scientists, they are sworn to veracity by their adherence to Scientific Method, their immutable and secularly sacred code of ethics and verification. 

Regrettably, the reality is to the contrary.  The shelves of research libraries are lined with scientific papers full of selective reporting, tweaking, distortions, presumptuous hypotheses, misleading conclusions, and outright lying.  When Dovid HaMelech branded the nations’ voice as vain, and their oaths as false, he did not mean to exclude scientists. 

We require no greater evidence than the blind adherence of the scientific elite to evolutionary theory as proof that scientists violate every axiom of their Method in support of their prejudiced conclusions.  Instead of testing their hypotheses and arriving at considered theories, they often work backwards from preconceived notions, discarding and distorting contrary information along the way.  Although there certainly are reliable papers and meticulous scientists, it is unwise to presume that their word is unwavering truth. 

Clearly, we must know that the author of a study is trustworthy, before giving credence to his conclusions.  Whereas Chasam Sofer (YD 101) embraces the veracity of Rambam to rule that the health concern of jointly cooked meat and fish had vanished in the centuries since the days of the Talmud, he dismisses the word of doctors who claimed that it had since returned in the centuries since the days of Rambam.  Changing nature is possible, but the word of the scientists in establishing that change is of dubious worth. 

We therefore must applaud the boldness of Harav Hagaon Asher Anshel Ekstein, the Belzer Dayan, who courageously states that scientists could certainly not be trusted in this case.  He notes that scientists do not believe that worms could form within fish flesh on their own (Presentation to AKO Conference, Shevat 5770).  Therefore, he correctly concludes that scientists cannot be objective regarding fish-flesh worms.  Since they believe that they must migrate to the flesh from the stomach, they will perforce misconstrue and ignore all contrary evidence, or rush to their preconceived migratory conclusions without convincing evidence of such.  Thus, the conclusions of the scientific papers presented should be judged as presumptuous at best, and fraudulent, at worst. 

Although most Poskim openly reject the authority of scientists to discredit Talmudic tradition, they are less bold when evaluating the validity of a Rav’s considered opinion, even when he has based his conclusions on the conclusion of the scientists, or has adopted equally conjectural methods.  It would seem that a Rav who is the mouthpiece for scientists, or who reaches conclusions in the same manner, is no more reliable than they. 

Rav Ekstein ignores an equally important point, perhaps because of his love of his fellow Yidden, which faults not scientists, but those who have used their conclusions as fuel in this firefight.  As best as this author could determine, there seem to be no more than a handful of papers, upon which the arguments of the prohibiting camp are based.  These few reports are all that has been disseminated as evidence of migratory worms, and seem to be all that is available in the public domain.  This paltry evidence of nature-change seems as mismatched against the weight of tradition and the Shulchan Aruch’s blanket ruling as is an untrained featherweight against a champion heavyweight fighter. 

We also note that even the scientists are quite unclear about the source of the flesh worms.  The CDC (Center for Disease Control) states unequivocally that intestinal worms migrate to the flesh only after the host fish dies.  They are not discussing migration after the catch, but migration when fish die in the open waters and wait a while before being ingested by a larger fish.  Thus, the scientists admit that contemporary worms cannot pierce the intestinal wall during a fish’s lifetime.  Accordingly, they would be perplexed when asked to explain the presence of flesh worms that clearly did not migrate there in the short time between catch and gutting.  Thus, scientific theory actually points away from migration! 

Rav Revach has presented his own evidence of migration, although he claims that it is all post-mortem.  Nevertheless, he has yet to present a well-documented paper, and his conclusions must therefore be carefully reviewed. 

Rabbanim and Spontaneous Generation We introduce this section with a disclaimer.  It is well known that spontaneous generation has been scientifically discredited by experimentation for the last 150 years.  Nevertheless, many teachings of Chazal hinge on a mechanism similar to spontaneous generation.  In our particular discussion, if spontaneous generation of flesh worms is not a considered explanation, we are forced to theorize about other possible sources of these worms.  The most prevalent explanation of internally generating worms that substitutes for spontaneous generation is that microscopic larvae develop within the flesh to visible proportions, and it appears as if they have spontaneously generated.  The problem with this hypothesis is that it concedes migration of the microscopic larvae into the flesh.  This is contradictory to the most essential element of the theory that permits flesh worms – that worms cannot migrate to the flesh from the stomach.  Therefore, instead, we embrace spontaneous generation in this presentation, for it is the only way to explain the words of Chazal, without saying that they erred.  We mean not to dismiss experimental evidence, but just to acknowledge that some mechanisms are hidden.  We are not certain how fish flesh seems to develop into worms.  We know that it cannot be because of migrating larvae, but experimentation has also discredited flesh transforming to worms on its own.  But, we are mindful that there is much that we do not know, and that Chazal were well versed in nature, beyond their experimental abilities.  Hence, we invoke “spontaneous generation” as the non-invasive mechanism by which the fish flesh transforms to worms, even though we are not certain what that mechanism is.  

We acknowledge that many Rabbanim seem duty bound to bend and twist in order to allow Shulchan Aruch and the words of Chazal to conform to accepted scientific notion.  (The theory of evolution is a notable exception, and does not evoke such contortions.)  In this and other instances, many Rabbanim cannot make peace with Chazal’s seeming embrace of spontaneous generation.  They therefore reinterpret Talmudic spontaneous generation as the development of microscopic eggs, spores, and organisms that have migrated or been deposited from elsewhere.  Thus, the invisible becomes visible, and appears to have self-generated.  In this case, these Rabbanim propose that microscopic larvae are ingested by crustaceans, which are subsequently ingested by the host fish; the still-microscopic larvae then migrate from the stomach to the flesh, where they develop and appear to have spontaneously generated. 

Unfortunately, this less-than-literal, and perhaps equally less-than-exact, contortion leaves considerable turbulence in its wake.  First, these Rabbanim have thereby adopted the argument of the prohibiting camp: there is migration from the stomach to the flesh!  Hence, these Rabbanim must be presumptuous, and somewhat fanciful, in order to validate their position.  They are forced to postulate that flesh worms develop from microscopic (and hence permitted), migrating larvae, while simultaneously claiming that the more fully developed and much stronger larvae that reside in the stomach cannot likewise pierce the abdominal wall.  This is nothing but fantastic and presumptuous, and it is as unbelievable as it sounds. 

The Rabbanim’s rejection of spontaneous generation also subjects them to both rabbinic and, l’havdil, scientific challenges.  A Gadol Hador has been rumored to rule that the size of migrating larvae is irrelevant.  Even if larva would be microscopic at the time of migration, the visible, grown larva is prohibited, since it developed from a migratory source.  In addition, the scientists are also not satisfied, for they claim that the larvae have grown to visible size by the time that they and their host are ingested by the next-level-up host fish. 

One respected Rav, who apparently realized the extent to which this argument is untenable, unfoundedly postulated that larger, already visible larvae migrate from the stomachs to the flesh, but that these prohibited larvae become permitted when they grow within the fishes’ flesh.  The scientists are satisfied, but the Poskim are not. On halachic grounds, this hypothesis is even more presumptuous and tenuous than the biologically untenable argument of microscopic migration, which it was meant to positively replace. 

We could attempt to explain this Rav’s position by acknowledging that the ingested larvae are not microscopic, without feebly suggesting that they become permitted within the flesh.  Instead, we would first need to say that developing larvae are kosher even within a non-kosher fish.  Although some have ruled that they are prohibited, there is no explicit ruling concerning this, and the law seems to be disputed.  In addition, we would need to say that the transfer of the larva from the crustacean to the host fish is not considered as if the worm left its growth environment, for then it would be prohibited.  We would need to distinguish between these worms and a worm that develops within post-harvest fruit and crawls out, directly into another picked fruit.  In the latter case, we rule stringently, even though the worm never was exposed to the outside.  In this case, we would have to say that the host fish is also considered a growing environment, for the larva continues to develop there. 

In order to resolve the first difficulty with this Rav’s position, we would propose that the larvae that enter through the nostrils are too small to penetrate the abdominal walls, but the ingested larvae within the crustaceans are larger, and they could penetrate.  Besides the problem that we are suggesting the opposite of what the Rav said, we would still need to contend that the worms that invade through the nostrils would never develop to penetration size.  And we also rely on two contested and unproven hypotheses: a) worms are kosher even when they develop within non-kosher fish, and b) the transfer of the worm from the crustacean to the host fish does not prohibit the worm.  Therefore, we are not able to reliably defend this Rav’s position.  

In summary, the case of the changing-nature, migratory camp is granted credibility by the reluctance and refusal of the opposing Rabbanim to take Chazal at their spontaneous-generation word.  Although there is nothing wrong with attempting to align scientific observations with the words of Chazal, we must be mindful of Ramban’s (Peirush LaTorah, Vayikra 16:8, at the end) castigation of those who adhere too religiously to the sciences: “ We must muzzle those who have become too educated in natural (science).  They follow the Greek (Aristotle), who denied all that he could not detect, and he and his students arrogantly thought that anything that he could not understand per his reasoning was false.”  We understand that experimentation has discredited the classic understanding of spontaneous generation, yet we are also mindful that the words of Chazal must stand without logic-bending contortions.  We must embrace non-invasive generation, as Chazal seemingly did, even if we are unaware of the mechanism by which it might take place.  Once we do this, we will be properly poised to appreciate the timeless nature of this ruling of Shulchan Aruch, and soundly reject the evidence presented in favor of the changing migratory nature of fish worms. 

The Migratory Evidence – Rav Ekstein concisely summarizes the migratory evidence.  First, worms identical to those found in the flesh are found in abundance in the fishes’ stomachs.  This proximate source of identical worms suggests that worms migrate to the flesh from the stomachs.  The prohibiting camp argues that Shulchan Aruch refers only to worms found exclusively in the flesh, about which we need not be concerned that they migrate to the flesh from elsewhere.  However, we cannot ignore proximate evidence of migration, and we must prohibit flesh-worms as suspected invaders from the stomach, when identical worms are present there. 

Second, Rav Revach presents ultra-violet-light-exposed pictures of tunnels within fish flesh from the worm-site to the stomach.  The prohibiting camp interprets this as evidence of migration from the stomach to the flesh. 

Third, the worms seem less predominant, and sometimes absent altogether, in farmed fish.  The prohibiting camp interprets this as evidence that contemporary worms do not spontaneously generate, for then they should be equally prevalent in farmed as in wild fish.  Rather, this disparity proves that the worms are migratory in the food chain of the worm-infested ocean waters, but absent in farmed fish, where the controlled and cleaner waters are worm-free. 

Fourth, and finally, the worms are more prevalent in the belly flaps of fish.  The prohibiting camp interprets this as proof of migration, for otherwise the worms should be evenly distributed within the fish’s flesh. 

Altogether, these arguments spawn the conclusion that contemporary worms are migratory from the stomachs, where they arrive after the host fish ingests smaller, crustacean or planktonian hosts of the larvae.  In turn, larger marine forms ingest the hosts of the larvae, until a marine mammal finally ingests them.  Then, the larvae attach themselves to the mammalian stomach lining, grow to maturity, and release their eggs, which are subsequently excreted to the ocean waters, and the cycle of the food chain begins anew. 

Refutation of the Third and Fourth Proofs 

The fourth proof is the easiest to brand as presumptuous, because it could well be that the belly flaps are more accommodating to worm generation than are other locations.  In a vacuum, stomach proximity might cause us to postulate about migration, but it is far from compelling enough to begin to challenge the universality of the Shulchan Aruch’s ruling.  (We will present below the minority opinion of one Rishon who understands that worms invade from outside the fish to its belly, and not to within its stomach.  Therefore, we would expect to see a predominance of belly worms, according to his opinion.)  

Before continuing, we note that Pri Megadim (Sif’sei Daas 84:43) and others comment that stomach worms are not certainly prohibited, but only out of doubt that they might have arrived from the outside.  It is also possible that they developed internally, as is the case with flesh worms.  So why should we be concerned about the presence of stomach worms, which might well have developed internally and be permitted?  We cannot permit them, because we are not certain, but that doubt should not foster speculation about possible migration of these possible invaders. 

We will also cite below, in our in-depth discussion of the Talmudic source, the opinions of Rishonim who permit flesh worms even when intestinal worms were present.  In addition, we will demonstrate that if we are concerned about worms in the stomach identical to those in the flesh, then we must extrapolate that flesh worms were never permitted, an impossible conclusion that contradicts Shulchan Aruch.   

The third proof of migration seems more credible, for what else could account for the noticeably lesser incidence of infestation in farmed fish than in wild fish?  (We interject that we have yet to see documented proof of this disparity of incidence.)  Again, although less comfortably, we contend that this argument is unconvincing when contrasted with Shulchan Aruch’s position that worms of his day did not migrate to the flesh.  Instead of postulating that nature has changed, we could argue that controlled farm conditions are less conducive to worm generation than are the wild, polluted waters of the oceans. 

That said, we admit that those who reject spontaneous generation have an easier time refuting this argument.  For if worms are indeed migratory, yet they emerge from microscopic migration, the disparity is fully explained by the egg-spawning environment of marine mammals and the host environment of smaller crustaceans and planktonians present in the wild.  (We will further discuss below the validity of ingested worms as the source of flesh worms.) 

Regarding disposition of the first and second proofs, we must first plumb the depths of the Rishonim’s writings concerning fish worms. 

The Contrary Opinion of Most Rishonim and of the Halachah – Over the past year, since the issuance of Maran HaGaon Rav Elyashiv Shlit”a’s Erev-Pesach-5769 proclamation concerning contemporary flesh worms, many have published articles outlining the view of the Rishonim and the Poskim regarding today’s state of infestation.  These articles, especially the more recent ones, are dizzying in the lengthy lists of Rishonim they cite in support of their particular positions.  We have found the actual distinctions between the opinions of the various Rishonim to be subtle, often misunderstood, and therefore sometimes misrepresented by the authors.  We will attempt to set the record straight. 

We begin with some background.  The Gemara (Chulin 67b) discusses two types of fish worms: darna and kokyana.  Many Rishonim interpret darna as a worm that resides between the skin and the flesh, which is revealed when the skin is removed, although some understand that it resides in the flesh itself.  These worms are permitted in fish, because they evolve from the permitted flesh of a kosher fish.  However, they are prohibited in kosher animals, because there they develop from unslaughtered flesh, which is prohibited.  (They might be similarly prohibited when developing in non-kosher fish, such as lower-chain crustaceans, for its flesh is prohibited – per Minchas Chinuch §163, cited by Darchei Teshuvah; Rav Wosner in Sheivet Haleivi 4:83 seems to reject this reasoning, as he offers other reasons why these worms become prohibited when ingested by the kosher fish.) 

All arguments concerning the status of contemporary flesh worms hinge on understanding the Gemara’s discussion of the other worm, the kokyana.  Hence, we are forced to elaborate.  First, we present the Gemara and some observations.  Next, we present the opinion of Beis Yosef and Shulchan Aruch, which is also the opinion of most Rishonim and the accepted halachah.  Finally, we present and explain the opinions of the dissenting Rishonim and Poskim. 

From the outset, as we might expect, the Gemara makes it clear that the status of the kokyana worm depends on whether it invades the fish from the outside, or whether it develops within the fish.  As an opening statement, Rav Sheishes, the son of Rav Idi, prohibits kokyana, because it invades from outside the fish.  Rav Ashi objects, stating that kokyana could not possibly invade from the outside, for the only place of residence for an invading worm is the rectum.  The Gemara then presents a similar, but opposite version, of the same discussion.  As an opening statement, Rav Sheisha, the son of Rav Idi, permits kokyana, because it develops within the fish itself.  Rav Ashi dismisses this ruling as redundant, since we could certainly have surmised on our own that kokyana is not an invader, since it is not found in the rectum.  Hence, it is elementary that it must develop within the fish.  The Gemara concludes that kokyana are prohibited, because there is, in fact, a way for them to penetrate to the stomach, where they are found: they could invade through the nostrils or ears of sleeping fish.  Therefore, we cannot be certain that any particular kokyana stomach worm developed within the fish itself, and we must forbid it out of concern that it is a prohibited invader.  

Rav Moshe Roth, the Karlsburg Dayan of Boro Park, points out that in the first version of the discussion, Rav Sheishes suggests that kokyana are invaders, without supporting evidence or reasoning.  It seems that Rav Sheishes had reason to believe that kokyana are invaders, most probably because he was aware that the waters were infested with kokyana. Nevertheless, Rav Ashi confidently permits kokyana, because he knows that they have no way to migrate from the stomach.  Thus, Rav Ashi was not concerned about internal migration, even though the host fish swims in kokyana-infested waters.  The Gemara concludes that direct, trans-nostril penetration to the stomach from the outside is possible, and kokyana are therefore prohibited as suspected invaders (Ohr Yisrael, Tishrei 5770). 

We notice something startling: the Gemara ignores and dismisses the obvious entry point for worms – the mouth!  It seems that the Gemara rules that worms would not survive feeding and subsequent digestion.  Meiri states this explicitly, suggesting that the Gemara does not mean to imply that there are whole worms in the rectum.  Rather, the Gemara’s point is that ingested worms will be dissolved by chewing and subsequent digestion, just as are the fish in which they previously resided prior to their ingestion. Accordingly, when the Gemara concludes that kokyana have a safe invasion route through the nostrils or ears, their destination is the belly area around the stomach, and not the inhospitable and destructive stomach.  Most Rishonim, however, understand that kokyana could survive in the stomach when reaching there through the nostrils, although they agree that they will not survive ingestion and digestion.  

Up to this point, Beis Yosef and most Rishonim (Rif, Ran, Raavan, Rabbeinu Tam, Rashba, Raah, Rav Yitzchak of Dura, Rav Baruch of Garmaiza, Raavad, Rosh, Rav Yisrael Isserlin, Rabbeinu Yonah, Or Zarua, Mordechai) establish that darna worms, located between a fish’s skin and its flesh, are permitted, since they develop from permitted flesh.  Kokyana worms, located in the guts, are prohibited, because they could have invaded through the nostrils from the outside, and are prohibited just as are any water worms.  What about fish-flesh worms? Those are neither darna nor kokyana, and according to Beis Yosef and many Rishonim listed above, the Gemara has not specifically ruled about them.  Beis Yosef rules that they are permitted, understanding that the Rishonim who prohibit gut worms would nevertheless permit flesh worms, for they certainly are not invading parasites. 

The Gemara perhaps had a tradition that skin-proximate darna are not migratory, and that kokyana are found only in the stomach, and not also in the rectum.  But how could Beis Yosef have been so certain about flesh worms, which the Gemara does not discuss?  Where has a tradition about their non-migratory nature been recorded, upon which he could base a lenient ruling?  Beis Yosef clearly understands the Gemara’s severe limitation of post-invasion habitats as indication that migration is out of the question.  Hagahos Ashri, citing Or Zarua and Mordechai, underscores this point by explaining that, “We are certain that [worms in the flesh] develop from [the flesh] itself, and that is why they are permitted.” 

Meiri also states something very similar regarding morna (synonymous with darna), which he understands to reside in the flesh.  After identifying their location within the fish he states, “It is certain that they are not invaders, but rather develop within the flesh.”  Some mistakenly argue that Meiri clearly means to say the opposite: that flesh worms are permissible only if we have a tradition that they are not migratory.  They argue that Meiri’s certainty is that of a specific tradition regarding morna, which the Gemara had.  This is incorrect, because Meiri contrasts morna to kokyana.  If morna is permitted because of specific tradition, whereas kokyana is prohibited for lack of tradition, he should have highlighted this as the difference.  Rather, Meiri portrays the difference as dependent on location: kokyana could invade to the liver and lungs (of animals) through the trachea, whereas morna certainly cannot invade, because they could not penetrate to the flesh.  Raah and Ran phrase their justification for the permissibility of fish morna similarly to Meiri, and they should be explained in the same manner.  Rashba’s words are explicit in this direction, although some unfoundedly and incorrectly interpret his definitive statement that flesh worms are not invaders as limited to situations where the worms are deeply embedded in the flesh.  Rashba mentions no such caveat, and any claim of this nature is purely inventive.  

Let us summarize this section.  Many Rishonim clearly state that worms cannot invade the flesh.  Shulchan Aruch, with his blanket, caveat-free ruling permitting flesh worms adopts this view, and none of the regular commentators contest it.  (Some incorrectly claim that Shach [84:43] rejects Shulchan Aruch’s ruling in this regard by explaining only why skin-proximate worms are permitted, but all could openly see that Shach says nothing of the sort.  If Shach meant to reject Shulchan Aruch’s blanket kosher certification of flesh worms, he would have said so explicitly, and not left this matter for later-day exposition of someone who wondered why Shach did not also discuss flesh worms while he was discussing something else.)  Also, we surmise from the Gemara that flesh worms are permitted even when the host fish swim in identically infested waters. 

The Opinion of Rashi 

Unlike other Rishonim, Rashi understands that the Gemara’s discussion of kokyana worms refers not at all to fish, but to animals.  Thus, the Gemara discusses kokyana located in the lungs and liver of an animal.  We proceed to outline the Gemara’s discussion according to Rashi, for it is instructive regarding basic presumptions about our concerns over the migratory nature of intestinal worms. 

Rav Sheishes begins by prohibiting kokyana, because they are ingested together with the animal’s food.  (According to Rashi, it is clear why Rav Sheishes proposes invasion without detailing his concern, since it is well known.)  Rav Ashi contests this assertion, because if it were correct, worms should have been found also in “the path of the rectum”.  In the previous section, we explained this inscrutable phrase in two ways, but neither literally interprets the entire phrase.  However, according to Rashi, the phrase is precise. 

Rav Ashi understands that Rav Sheishes does not mean to propose that the ingested worms penetrate to the liver through the walls of the digestive tract, for then the entire animal would be treifah.  Rather, he understands that Rav Sheishes proposes that the ingested worms travel to the end of the digestive tract, exit through the rectum, and then turn around to bore through the flesh until they reach the liver.  From there, according to Talmudic understanding, they could penetrate to the lungs without puncturing them.  Rav Ashi argues that the journey from the rectum to the liver is quite long, and therefore it is impossible that some worms would not have been left along the path.  Therefore, we must discard this possibility, and we conclude instead that the worms developed within the liver and lungs. 

The Gemara concludes that these worms are prohibited, because they penetrate to the lungs and liver through the nostrils.  Rashi explains that we are no longer troubled by the absence of worms along the path to the rectum, for we now propose that the kokyana take a different route to the liver and lungs. 

According to Rashi, we deduce two important lessons.  First, since kokyana worms are ever-present in the food that the animal ingests and also in its intestines, we cannot presume that worms elsewhere in the animal develop internally without some form of proof that the intestinal worms do not migrate.  Along Rav Sheishes’s proposed invasion route from the rectum, the absence of straggler kokyana is evidence that the route is not traversed.  Second, we note that there is no concern that ingested worms pierce the abdominal wall, even though they are found in abundance within the intestines.  That is why Rav Sheishes was forced to propose a lengthy and circuitous route for the kokyana, because the shorter route through the abdominal walls is not possible. 

This second point is derived from the laws of treifus, where the presence of a worm within the intestines or other organs does not generate concern that it punctured a critical organ.  Clearly, this is an act of G-d’s kindness, denying ubiquitous worms the ability to inflict such damage.  This is true for animals, but what about fish?  Perhaps we cannot compare the two, and intestinal fish worms are suspected of penetrating the intestinal walls, unless proven otherwise.  On the other hand, punctured intestines render an animal treifah because it cannot survive such a wound.  Although fish cannot become treifah, they still require healthy organs in order to survive.  May we not extrapolate from the laws of treifus that any creature, including fish, cannot survive if its intestines are perforated? 

Beis Yosef answers this question in the affirmative, for he presumes without explicit mention that Rashi permits fish-flesh worms.  Beis Yosef only finds it necessary to mention that Rashi would also prohibit fish-stomach worms, even though Rashi has no Talmudic precedent for validation of the nostril-to-stomach invasion route discussed for fish.  Thus, despite the presence of intestinal worms, Rashi permits flesh worms, for there is no concern that worms could penetrate any intestinal wall, even that of a fish.      

Refutation of the First Proof 

Before proceeding to scrutinize the first two proofs of contemporary migration, we cite the opinion of Rav Yisrael Isserlin in Hagahos Shaarei Dura (§47).  He permits white shwibrin worms that we observe burrowing from the surface deep into the flesh of fish, for we are certain that they originate within the fish flesh.  Rav Isserlin understands that even when we witness penetration of these worms, we may presume that they were originally internal, since we often find them in the flesh, and are therefore aware that they develop within the flesh.  Rav Isserlin is not concerned that these burrowing worms are originally external, and hence prohibited.  Regarding flesh worms, we presume that they developed internally even when the possibility of external penetration is present! 

According to some versions of Hagahos Shaarei Dura, Rav Isserlin permits even those shwibrin found inside the stomach.  This is an extension of his above-cited ruling, for here the worms are not found within the flesh, yet he nevertheless says that we presume that they originate from the flesh, and did not invade through the nostrils. 

Now, we are prepared to examine the first proof.  The anisakis worm, today’s most nefarious invader, is commonly found in fish stomachs, and therefore presumed to have originated outside the fish.  Does the presence of identical, prohibited worms in the stomach obligate us to be concerned that worms imbedded in the flesh migrated from there?  According to one version of Rav Isserlin’s ruling, we presume the contrary: that the anisakis worms in the stomachs are kosher, having migrated from the flesh.  But even according to the common version of Rav Isserlin’s ruling, we see that he favors internal generation to possible invasion.  This is certainly true when considering the possibility of invasion from the stomach, for we would then also have to assert that contemporary worms have newfound trans-intestinal migratory powers.  We also note that both Beis Yosef and many Rishonim reject migration out of hand, even when the flesh worms found are identical to those present in the local waters (per Rav Roth’s proof, above).  These worms could penetrate to the stomach, yet we are not concerned that they migrate from there to the flesh.  So why should we be more concerned when we actually find them in the stomach? 

Also, what would the science-adherents within our midst say?  They reject anything akin to spontaneous generation, and agree that worms never originate in the flesh.  Yet they claim that we cannot permit flesh worms without specific tradition of their non-invasive nature.  Where do they originate?  They begin as discharged eggs in the ocean, developing as larvae through ingestion by successively larger hosts. Hence, proponents of the flesh-invading food-chain theory cannot permit a single flesh worm without definitive evidence that the larva does not develop beyond microscopic size before it is ingested, and no such evidence or tradition is available.  Therefore, according to their claims, we arrive at the illogical and impossible conclusion that the ruling of Shulchan Aruch never applied to a single worm in history! 

Perhaps for this reason, and perhaps for others, some adopt a multi-tiered approach.  They acknowledge that we embrace spontaneous generation as Halachah, and therefore we permit most flesh worms.  They object only to permitting worms such as anisakis, since identical worms are proximately present in the fishes’ stomachs.  Although proponents of this argument thereby avoid being backed into the corner of faulty logic described above, they still must explain why they are concerned about proximate stomach worms but not about outside worms, all of which could penetrate.  If it is an axiom that worms cannot migrate to the flesh, then both should be permitted!  And if it is not an axiom, and we could rely on intra-muscular generation only when invasive possibilities have certainly been ruled out, then both should be prohibited! 

We challenge the assertion of the two-tiered proponents that they have investigated the intestines of fish infected with worms other than anisakis, and that they have never located a single identical worm in the stomachs of these fish.  How many intestines have they dissected?  These are ordinarily discarded in a fish factory.  Did they, or those that have made these claims, have the patience, manpower, and budget for such a commercially irrelevant search?  And since most of these worms are invisible without special lighting and preparation, how did these two-tiered advocates arrive at their conclusions that these intestines, in contrast to those of anisakis-infested fish, were worm-free?  Have they published any papers detailing the results of this research?  Rather, it is clear that their claim of worm-free intestines in other cases of flesh infestation is nothing more than hopeful conjecture, and therefore they cannot escape the conclusion that their arguments prohibit all flesh worms, then and now. 

Also, do they mean to imply that we could presume worm-free conditions in the surrounding waters until we detect identical worms there?  If the presence of even a single worm outside spoils the permissive ruling, then should we not need to inspect the waters, and in addition, at least catch and spot-check lower forms of local marine life?  How could we cavalierly ignore the possibility of invasion, when we might mistakenly be permitting a Torah prohibition? 

The answer is simple: there is no such concern according to Halachah.  When we find a flesh worm, we may confidently surmise that it developed internally, per the blanket ruling of Shulchan Aruch.  Any contention to the contrary results in impossible rejection of Halachah. 

Proponents of the two-tiered approach – that we are concerned over the invasion of some worms, but not about others – would do well to learn from Rav Yitzchak of Dura (Shaarei Dura §47 and §52).  Rav Dura accepts the ruling of Raavan that internally developed flesh worms are permitted, yet understands that the Gemara ultimately rejects the utility of this ruling by noting that we must be concerned about the possibility of trans-nostril invasion.  Therefore, even though internally generated flesh worms are permissible, we are not able to separate the natives from the immigrants, and we must prohibit all worms. 

Rav Dura’s minority ruling is rejected by Shulchan Aruch, who codifies the permissibility of flesh worms as Halachah, without qualification.  But we remain with an important lesson.  If concern about the possibility of invasion trumps the universality of internal sourcing, then we must prohibit every flesh worm, without exception.  There is no acceptable middle ground.  Hence, claiming that we must be mindful of possible invasion is tantamount to completely rejecting Shulchan Aruch! 

Rejection of the Second Proof 

The second proof is based on Rav Revach’s testimony and pictorial demonstration that tunnels exist between the imbedded worms and the stomachs.  Before delving into the validity of this proof, we question its authenticity.  How many worms were identified, and how many of them had tunnels connecting their location to the stomachs?  Rav Revach states that he exposed these tunnels with ultraviolet light in one shipment of Japanese salmon.  He states that he found the tunnels in some fish, but not in others, without providing any other details.  How does he explain the lack of tunnels in some (many?) fish?  Has he searched for these tunnels in other shipments without success?  Could these tunnels not be the result of salmon that was held ungutted for longer than usual, thus allowing for post-mortem migration that is not usually the norm? 

The publicly available papers do not mention anything about these tunnels.  However, they do mention that the anisakis larvae are dormant within the flesh, and that a cyst surrounds them.  We postulate that even if these worms were migratory, all migratory tunnels would have closed and healed in the same time in which the larva is embedded within a cyst.  Therefore, even if tunnels exist, they are not indicative of ante-mortem migration.  We acknowledge that this hypothesis is unproven.  But even if it is incorrect, the paltry evidence of tunnels presented points to postmortem, and not to ante-mortem, migration, which do not explain at all the presence of encysted larvae within the flesh. 

Even presuming that the Rav Revach’s observations are sound, and his theory that they are evidence of migration true, we question his directional conclusions.  How do we know that these tunnels are evidence of migration from the stomach to the flesh?  Perhaps they are evidence of the opposite – of worms migrating from the flesh to the stomach!  Rav Revach could retort that since the worm is found in the flesh, it is more likely that it emanated from the stomach, rather than that it traveled to the stomach, only to return to the flesh.  But Rav Isserlin stands in opposition to this presumption, ruling that we presume a worm emanated from the flesh even when we observe it boring into the flesh from the surface!  Rav Revach’s assertion therefore requires further verification, and even if correct, it is refuted by a Rishon. 

Dissenting Opinions 

The prohibiting camp notes that not all Rishonim and Acharonim permit fish-flesh worms, in part or at all.  They claim that it is therefore appropriate or meritorious to act stringently according to these minority opinions, even though Shulchan Aruch and its regular commentators reject them.  They base their claim on Shulchan Aruch’s citation of one of these minority opinions, which they interpret as Shulchan Aruch’s suggestion that we should be stringent, although we are not so obligated.  This proof is far from airtight, and practically, it was always the custom to ignore this minor opinion, as Rama records. 

In this section, we will first prove that, in fact, Shulchan Aruch does not cite any minority opinion on this topic.  We then proceed to explain the various dissenting opinions, for there is much confusion regarding what their actual positions are.  Nevertheless, the ensuing discussion is purely academic, for none of these positions are adopted as halachah.  Therefore, readers uninterested in these details will not miss anything of halachic import if they skip to the next section. 

Rambam (Ma’achalos Asuros 2:17) issues a very enigmatic ruling: “A worm found in fish guts, or in the head of an animal, or in meat (even long after slaughter), is prohibited.  But if salted fish becomes wormy, a worm inside it is permitted.”  Rambam seems to understand that the Gemara’s approval of fish darna refers only to postmortem generation, and not generation within a fish’s life.  (Similarly, its prohibition of animal darna refers even to postmortem generation.)  If so, why does Rambam limit his prohibiting ruling to worms found in fish guts, when even skin-proximate and flesh-resident worms are prohibited?  Rav Efrayim Margolis (Beis Efrayim Yoreh Deah §25) suggests that Rambam did not recognize ante-mortem worms within fish flesh, and therefore did not discuss them.  Magid Mishneh explains that Rambam holds that only dead flesh will generate worms.  Therefore, he concludes, worms found anywhere in a freshly caught fish are prohibited, because they could not have generated within the fish, but rather must have invaded from the outside.  Rambam discusses only gut worms, for those were all that were prevalent in his days, but Magid Mishneh reveals the law for any worms that one day might be found in the flesh. 

According to this approach, we have an additional understanding of why Rav Sheishes opens the discussion about kokyana by stating that they are certain invaders (see above, The Contrary Opinion of Most Rishonim and of the Halachah).  Since live flesh cannot generate worms, the only possibility is that kokyana are invaders.  This could be Rambam’s source for his position. 

Thus, we see that Rambam disagrees with Shulchan Aruch’s permissive ruling regarding flesh worms in freshly caught fish.  Nevertheless, we see that Rambam’s reason is not that he is minimally or maximally concerned about invaders, but rather because ante-mortem worm generation is impossible, and therefore all worms must be invaders.  Hence, Rambam (per Magid Mishneh) actually indicates the opposite of what the opposing camp claims.  We could happily dismiss claims of invasion and migration if internal generation were possible.  But before death, worm generation is impossible, and our only choice is to recognize that somehow the worms invaded. 

The prohibiting camp claims that Shulchan Aruch cites Rambam’s opinion prohibiting ante-mortem fish-flesh worms as a minority, dissenting opinion.  This claim is incorrect, as it is based on two inaccuracies.  First, Rambam does not say anything about flesh worms.  It is Magid Mishneh who posits that when we are faced with a conflict of dually improbable live generation and worm migration, we side with migration.  But Beis Yosef could disagree with this, and claim that Rambam would permit such worms, siding with generation over migration.  Perhaps ante-mortem generation is possible from flesh that has atrophied, and behaves as dead flesh.  Therefore, Shulchan Aruch cannot cite Rambam’s dissenting opinion, since in his opinion Rambam does not dissent.  (B’eir Hagolah disagrees with this point, as he understands that Magid Mishneh’s explanation of Rambam is indisputable.) 

Second, Shulchan Aruch cites Rambam only regarding his prohibitive position regarding postmortem worm generation in rotted animal flesh.  Even if Magid Mishneh is correct about Rambam’s position regarding fish-flesh worms, Beis Yosef does not bother to mention it, and therefore he is certainly not recommending it for meritorious stringency. 

Rav Baruch of Garmaiza (Sefer Haterumah §36) takes a position identical to Magid Mishneh’s understanding of Rambam. 

Rabbeinu Yonah (Issur v’Heteir 41:9) seems to have been familiar only with skin-proximate worms, which he permits because they internally generate.  However, he cites Rav Yitzchak of Dura’s opinion that worms are permitted only if found in a freshly opened fish, but not if found afterwards in the fish’s pieces. 

We note that Rav Yitzchak of Dura does not mention anything about a time lapse that could create an opportunity for invasion of an otherwise worm-free piece of fish.  In fact, we noted above that it seems that Rav Yitzchak prohibits all flesh worms, because they might have invaded through the nostrils and migrated.  Nevertheless, Rabbeinu Yonah understands that Rav Yitzchak does not say this.  Since Rabbeinu Yonah is quoting Rav Yitzchak, it seems that he has a different version of Shaarei Dura than ours. 

Maharshal (Yam Shel Shlomo, Chulin 3:104) understands Rav Yitzchak in an even more diminutive way.  He says that Rav Yitzchak permits all flesh worms, but we need to be concerned that prohibited gut worms should not find their way to the flesh while we are cleaning and cutting the fish. 

Thus Rabbeinu Yonah and Maharshal discuss post-catch contamination, and do not at all propose that we cannot permit internally generating flesh worms if a concern over possible invasion exists.  This is in direct opposition to the understanding of the prohibiting camp.  Only Rav Yitzchak of Dura discusses this topic, and Shulchan Aruch rejects his opinion. 

Finally, the prohibiting camp presents three Acharonim who rule that flesh worms are not permitted if a possibility exists that the worms are actually invaders that migrate to the flesh: Bach, Orach Mishor (94:9), and K’neses Hag’dolah (94:101).  We note again that our discussion of these Acharonim is purely academic, for their opinion is not adopted in halachah. 

Bach states that Rabbeinu Tam (who permits flesh worms because they generate within the flesh) concurs with Rabbeinu Yonah, Rav Baruch, and Rav Yitzchak.  Rav Margolis considers this to be an incorrect oversimplification, for as we have explained above, each of these four Rishonim holds something different than the others.  Certainly, Rabbeinu Tam and the majority of Rishonim who side with his permissive ruling, do not mention any caveats. 

Orach Mishor outdoes Bach by including Maharshal’s opinion as identical to the purportedly identical opinions of the four Rishonim.  This seems to be incorrect, for Maharshal discusses a very limited circumstance of post-catch contamination. 

K’neses Hag’dolah mimics Orach Mishor’s approach along this line, and it is equally problematic. 

The prohibiting camp strenuously argues that we must follow the stringent opinion of these three Acharonim, but they do not acknowledge that all three opinions are problematic and seem to be incorrect.  They also do not acknowledge that all these opinions are not mentioned by the standard commentators, and that they all seem to be rejected by Halachah.  Although it is certainly a mitzvah to properly explain these three difficult opinions, it is not reasonable to demand that we must follow them. 

In summary, Halachah rejects all the above opinions, and there is no reason at all to be stringent regarding fish worms, when Shulchan Aruch and the commentators have not even hinted at any limiting conditions or caveats to this ruling.  In addition, the opinions of many of these Rishonim and Acharonim are poorly, and often incorrectly, understood, and it is certainly unreasonable to expect the public to abide by faulty interpretations. 

At this point, we note that some cite Chazon Ish’s (14:6) discussion of surface fish lice as proof that he holds that we cannot rely on internal generation when invasion is a possibility. Chazon Ish states that we cannot permit surface lice on fish if the possibility exists that they attach themselves to the skin from the open waters.  Hence, it seems that Chazon Ish withholds approval of worms until we are certain that they could not have arrived from the outside.  We feel that this precedent cannot be applied to flesh worms, since we have Talmudic proof that we need not be concerned about possible migration.  Only regarding surface worms is there no tradition, and therefore Chazon Ish rules that we cannot permit them unless we are certain that they are not immigrants. 

A Biological Proof to the Contrary – According to scientists, the anisakis is ingested by fish when they eat lower-food-chain-level crustaceans and planktonians, in which the larvae have already taken up residence.  Since the consumption of these worms is somewhat of a constant throughout a fish’s life, we would expect to find worms in various stages of migration within fish flesh.  From the reports that we reviewed, it seems that these larvae are all encysted, and not found in migratory positions.  This seems to indicate that these worms are not migratory, but that they develop within the fish, and are subsequently surrounded by cysts. 

The author acknowledges that he is not in any position to research marine biology, and that he is able to review only the same scant few publicly available papers that have been read by all who have written about this topic.  Such paltry research regarding this point is far from conclusive, but it is as comprehensive as is currently feasible. 

Postmortem Migration – Some have argued that contemporary, industrial catch methods promote migration of intestinal worms to the flesh.  Their logic is that the intestinal tissue weakens after death, and that allows the worms to migrate, even though they could not have migrated during the fish’s life.  If correct, this proposal resolves almost all of the difficulties faced by the prohibiting camp.  Since migration to the flesh does not occur during a fish’s life, we are in full conformance with Halachah.  Nevertheless, fish must be inspected for worms, for we are concerned about post-catch migration. 

This argument, even if properly demonstrated, does not at all explain the presence of encysted larvae, so not much is gained by forwarding it.  All the same, we will analyze this suggestion, and we begin with a question.  In Talmudic days, refrigerating and icing the catch was impossible.  We therefore presume that fishermen worked for a good part of the day, or for an entire day, and then brought their ungutted fish to the market.  Before they were sold and gutted, a day or two from the catch could have passed, yet Shulchan Aruch does not put an expiration date on his ruling permitting flesh worms!  And if proof of this is required, the Gemara explicitly discusses gutting fish the day after, and sometimes two days after it was caught (see Beitzah 24b and Shulchan Aruch Orach Chayim 515).  So if Chazal were not concerned about post-catch migration even if fish were left unrefrigerated and ungutted two days after the catch, why should we be concerned about it nowadays if fish is left ungutted for a few hours, and refrigerated throughout? 

The only answer to this question is that postmortem migration cannot account on its own for the incidence of the anisakis in the flesh.  Rather, it generated during the fish’s life, and did not arrive there in the few hours that it was ungutted after the catch.  Although we have already proven this approach inadequate to address the difficulties faced by the prohibiting camp, we proceed nevertheless to further analyze the evidence of postmortem migration.  

Rav Revach has demonstrated that worms migrate from the stomach to the flesh after the catch, but the circumstances of this observed migration are quite unclear.  Has it been demonstrated that worms migrate from complete stomachs, or only from mostly dissected stomachs?  How many experiments were conducted, and what were the results?  Were the successful experiments contrived?  Has the complete penetration of even a single worm been demonstrated? 

Rumor has it that 10,000 fish from a certain location were gutted immediately after the catch, and no worms were found in their flesh.  In the same location, under the same conditions, the guts were not immediately removed, and the flesh was infested.  This experiment is meant to prove that the only source of flesh worms is postmortem migration. 

We have some questions about this experiment.  What time frame is considered to be “immediate”?  How long was gutting delayed in the other fish?  How were 10,000 fish immediately checked after the catch? 

Even if the details of this experiment are impeccable, we must question its relevance.  Even the prohibiting camp concedes that there are areas and species that are worm-free, so what does inspecting fish from such a location prove?  Also, the papers all concede that lengthy delay of gutting could lead to migration of the stomach worms to the flesh.  So what does inspecting delayed-gutting fish prove?  

Some have argued that even short-term refrigeration allows the worms to migrate.  We note that the reports indicate the opposite: intense cooling, as is the norm for post-catch fish, retards migration, and a few hours or even days should not be sufficient to explain the incidence of anisakis observed.  We also challenge the notion that packing ruptures the intestinal membranes, as fishermen would not want to press their fish to this extent, for it would ruin their catch.  Some experts have testified that the bottom layers of fish caught in giant nets are subjected to intense pressure, but that would account for only a small incidence of intestinal rupture. 

Conclusions – In this article, we have noted and demonstrated the following:

• There is not an abundance of scientific research regarding flesh-resident anisakis
• The non-scientific evidence presented lacks detailed reporting ordinarily associated with research papers, and is unconvincing
• Scientific claims that anisakis migrates from the intestines to the flesh is pure conjecture, without any scientific evidence
• According to the CDC, anisakis do not pierce live, intestinal walls, and their scientists would be at a loss (if they were consistent and honest) to explain the presence of the flesh worms that we encounter, which clearly did not migrate there after the catch
• Scientific conjecture that flesh worms are migratory emerges from scientists’ prejudiced rejection of any other possibility.  If they would validate the words of Chazal that migration is not necessary to explain the presence of flesh worms, scientists would not have arrived at their migratory conclusion.  We cannot accept their conclusion, for it is founded upon complete rejection of Chazal’s word
• Shulchan Aruch and all its standard commentators clearly rule that we need not be concerned about migration from the intestines, and any claim that things have changed requires impossible authentication
• Many Rishonim state explicitly that we are certain that worms do not migrate from the intestines to the flesh
• Stomach worms are prohibited only out of doubt that they might be invaders.  This doubtful status is insufficient to create concern over their possible migration to the flesh, even if such concern would exist
• We proved that worms do not migrate out from an animal’s intestines, for they would render the animal treifah.  We surmise from Beis Yosef that the same is true for fish, since migrating worms would puncture the intestines, and ultimately kill the fish
• There are three Rishonim who reject the possibility of live flesh transforming to worms, but their opinion is rejected by Halachah
• There is only one Rishon, Rav Yitzchak of Dura, who rejects internal generation when a concern of invasion exists.  His opinion is rejected by Halachah
• Three Acharonim suggest that we should prohibit flesh worms if the possibility of invasion exists, but they are rejected by Halachah, and their opinions are plagued with some technical difficulties
• Those who propose that we should be concerned about possible migration unless we have a specific tradition to the contrary cannot escape the illogical consequence of their proposal that all flesh worms, anasakis and otherwise, are prohibited, since all could invade and migrate.  This results in impossible, complete rejection of Shulchan Aruch’s ruling permitting flesh worms, then and forever
• According to all scientific evidence, identical stomach worms are always present when flesh worms are present.  Since no authority throughout the centuries has mentioned the presence of stomach worms as a counterweight to Shulchan Aruch’s permissive ruling, we conclude that they were not concerned about it.  Claims that there are no intestinal worms when flesh worms other than anisakis are present are not based on any scientific evidence
• If stomach worms were migratory, we should expect to find worms within the flesh in various stages of migration, and we do not
• It is difficult to claim that postmortem migration is solely responsible for incidence of flesh-resident anisakis, because the worms could not have become encysted in such a short time
• Chazal permitted fish, and presumably its flesh worms, at least two days after the catch, so it is difficult to claim that delaying gutting for hours is why flesh worms are prohibited today when they were permitted centuries ago