Signs of a Kosher Fish

The Torah requires that Kosher fish must have both scales and fins. The fact of the matter is (as the Talmud says - Chulin 66b) that all fish with scales also have fins, so in practice Kosher fish are identified by their scales. Obviously, crustaceans (such as lobster) and other shellfish (such as clams) are not Kosher because they lack scales. All “scales”, however, are not Halachikally equal. Halacha defines a fish scale as a growth on the side of a fish similar to a fingernail – it must be removable without damage to the skin of the fish. Sturgeon, although it has primitive bony plates on its sides, is not considered Kosher because the scales cannot be removed without damaging the flesh. Sharks are similarly not Kosher, because their skin is covered with tiny teeth-like armor, which are not considered scales at all. 

The first step in determining a Kosher fish is verifying that it has a Kosher scale. Although many Kosher fish are completely covered with scales, Halacha requires only a minimum number of scales to accord a fish Kosher status (see Y.D. 83:1). Tuna, for example, have very few scales, yet are nevertheless considered a Kosher fish. Two additional factors, however, serve to complicate these determinations. First, a given species of fish may be known by five or more names, some of which are common to known Kosher species. “Rock Salmon”, for example, is a non-Kosher fish (otherwise known as Atlantic Wolfish), and bears no relationship to the common Kosher species of true salmon. Furthermore, although Halacha requires an accepted Kosher tradition for considering birds (and according to many authorities, even animals) as Kosher species, no such Halachik requirement exists for fish.  Each of the hundreds of species of fish on the market may be evaluated as to its Kosher status, even if it is newly discovered. It is therefore critical to evaluate a given species very carefully before making a determination as to its Kosher status.

Processed Fish - Fish Fillets

Since Kosher and non-Kosher fish can be very similar, Halacha requires that fish may not be eaten unless they have been inspected to ensure their Kosher status.  As such, one may not purchase fish fillets (where all of the skin has been removed) without a reliable Hashgacha, since the filet is no longer identifiable as a Kosher species.  Fish roe may also not be used without such supervision for the same reason (true caviar comes from sturgeon and is not Kosher in any event). There has been much discussion as to the Kosher status of canned fish (such as tuna and skinless sardines), in situations where the supervision of the cannery is based upon spot checks and each fish is not checked by the Mashgiach.  Many authorities are reluctant to accept the Kosher status of such fish (see Igros Moshe Y.D. II:8, IV:1).

One possible approach to dealing with processed fish is based upon the ruling of the Shulchan Aruch (Y.D. 83:8), which states that if the flesh of the fish is red then it can be assumed to be from a Kosher species.  [This ruling is predicated upon the understanding that all red fleshed fish are Kosher, an assumption questioned by the Shach (ibid, s.k. 27).]  While this approach would seemingly solve concerns relating to red fish, modern food technology may have compromised its application.  Much of the fish consumed today is raised on “fish farms”, ponds or other enclosed waters where fish are segregated and fed a specific diet.  It has been found that if certain foods containing red pigments are fed to certain fish, their otherwise white flesh develops a red color.  This is indeed the process used to produce “salmon trout”, which is a normal trout that has been fed red pigments. Once such a process has been found to circumvent nature, it becomes very difficult to maintain the Halachik rationale that all red fish must be Kosher.

Processed Fish - Canned

Canned fish poses another Kashrus concern based upon the rules of Bishul Akum. Halacha states that a Jew must be involved in the cooking process of many foods, a requirement that is addressed by reliable Hashgachos. Unfortunately, most fish canneries are located in parts of the world that do not lend themselves to full-time (or even significant) involvement by the Mashgiach.  A number of Halachik approaches have been explored to address this issue (based upon the method by which the fish are cooked and whether this type of fish is included in the restrictions of Bishul Akum), but many authorities do not accept canned fish that has not be cooked with the involvement of the Mashgiach. To address both of these concerns, many Kosher canned fish now bear a specific designation that they have been prepared under full time supervision.

Processed Fish - Smoked

Smoked fish poses another interesting Halachik concern related to the rules of Bishul Akum, and one that illustrates how deceptive food terminology can be.  One of the general rules of Bishul Akum is that it applies only to food that is cooked with heat – smoked food is not subject to this restriction (Y.D. 113:13).  It would therefore seem a simple matter to certify smoked fish – were it not for the fact that the fish is actually baked!  Most commercial smoked fish is actually baked in a large oven, with a small amount of smoke added at the end of the cooking cycle for flavor.  The smoking process that is free of Bishul Akum concerns involves cold smoke – a tedious and expensive process.  Another point that should be noted is that that fish smoking plants often smoke sturgeon, eel, and other non-Kosher fish, making a reliable certification for smoked fish an absolute imperative.

Kosher Lobster?!

The Talmud also teaches us that for every non-Kosher food there exists an equal and opposite Kosher version (Chullin 109b).  Modern food technology has indeed given a new twist to this concept.  While lobster, shrimp, and crab may not be Kosher, imitation versions of these non-Kosher staples can now be obtained with excellent Hashgacha. Surimi is an ancient Japanese process by which minced fish is converted into a protein base and used to produce a variety of foods. Today, Kosher surimi (produced under supervision, of course) is used to produce imitation crab legs, lobster, and shrimp – and is deemed a reasonable facsimile of the real thing!

Fish Oil

Other interesting application of ichthyology in modern food technology relates to fish oil.  In many parts of the world, fish oil is used as we use vegetable oil – to make margarine, for cooking, etc.  The fish used to produce fish oil are certainly not inspected by a Mashgiach, and such oil generally not accepted as Kosher. While this use of fish oil has not yet come to North American shores, a modern version of a child’s nightmare has. One time-honored fish oil was cod liver oil, which provided as a rich source of vitamins.  Its use has become less common due to improved diet and vitamin fortification of foods. Research now shows, however, that certain fatty acids found in other types of fish oil may have significant benefit in reducing heart and other problems – components commonly referred to as Omega-3 fatty acids.  While these often come from Kosher fish, one should consult a Halachik authority to determine their appropriate use.

Anchovies & (Fish) Gelatin

Derivatives of fish often wind up in unexpected places – both ancient and modern –  and may pose both health and Halachik concerns.  On one hand, classic Worcestershire sauce contains anchovies as part of its flavoring base, which raises issues as to its acceptability in flavoring meats (fish may not be eaten together due to health related concerns discussed in the Talmud).  

On the other hand, modern food technology has developed a new way of producing gelatin.  Gelatin is an animal derived protein, used as the base of gel-type deserts and gummy-type candies and as a gelling agent in Swiss-style yogurt. Gelatin is generally produced form animal skins and bones, and volumes have been written by Halachik authorities discussing the Kosher and/or Pareve status of gelatin derived from non-Kosher species (pigs), non-Kosher slaughtered animals (beef), and Kosher slaughtered animals. The generally accepted position adopted by Kashrus authorities is that only gelatin derived from Kosher slaughtered hides and bones can be considered Kosher. Such Kosher beef-based gelatin is quite expensive, and for this reason Kosher versions of products normally containing gelatin are often reformulated to use other materials (typically seaweed derivatives such as agar agar and carrageenan). Recently, however, companies have developed a gelatin derived from Kosher fish, and many candy products are being developed to take advantage of this newly available Kosher alternative. Persons allergic to fish, however, should check the label for fish gelatin.

Gefilte Fish - (not "Filtered Fish") A Gastronomic Delight!

It is always interesting to note how the scrupulous observance of Halacha affects all aspects of our lives. It has long been a custom to eat gefilte fish on Shabbos.  Although the gastronomic considerations of this delicacy may seem the most obvious, the real reason for this custom lies a bit deeper. Shabbos is a day of rest where many types of labor are prohibited. One of the activities in which one may not be engaged on Shabbos relates to the separation of chaff from grain, which is known in Hebrew as Borer. This restriction extends to many types of separation, and the rules governing which types are permitted and which are not can be quite complicated. Eating fish is a common situation where Borer becomes a problem, since fish is often served whole and bones were not removed before serving. In order to avoid this concern, a custom developed whereby the fish was filleted, ground, and stuffed back into the skin and then cooked. The resulting delicacy – gefülte (stuffed) – fish was then presented at the Shabbos table in a beautiful presentation – ready to be eaten without worrying about Borer! 

Even though we often eat gefilte fish sans skin, the origin of the custom is an apt testimonial to the care that the Jewish people have historically taken to abide by all Mitzvos. May be it in the merit of customs such as gefilte fish and the strict adherence to Kashrus issues which fish present. that we grow in holiness which the Jewish people represent!

Rabbi Zushe Blech is Kashruth Consultant

Rabbi Zushe Blech of Monsey, NY is a well-known Kashrus expert and writer on Kashrus topics. When he lived in Chicago, Rabbi Blech was a member of the Kashrus Committee of the cRc. 
Article printed with permission of Rabbi Blech.