Kosher Fish Production: Getting Into the Stream of Things

A Q&A on Kosher Fish Production

So your fish processing company is thinking about becoming OU kosher, but you have some questions? We can help!

All kosher fish must have (fins and scales). Furthermore, the scales must be capable of being removed without tearing the fish’s skin (See Rema Yoreh Deah 83:1). It is not unusual for some fish to meet the first two criteria and not the third. Sturgeon, which is a very common type of fish, is a prime example. A sturgeon has scutes, which are similar to scales, but are embedded and cannot be removed without tearing the skin. Therefore sturgeon is not kosher. 

The Torah establishes two criteria to determine which fish are kosher. The fish must have fins and scales. The scales must be easily removable without damaging the skin. [Generally, scales on kosher fish are either thin, rounded and smooth-edged (cycloid) or narrow segments that are similar to teeth of a comb (ctenoid)]. All shellfish are prohibited. Unlike meat and poultry, fish requires no special preparation. Nonetheless, the fish scales must be visible to the consumer in order to establish the kosher status of the fish. Therefore, filleted or ground fish should not be purchased unless properly supervised, or the fillet should have a skin tab with scales attached. Furthermore, purchasing fish in a non-kosher fish store is problematic – even if the scales are intact and Rabbinic guidance should therefore be sought.

The basics: Kosher law requires a fish to have scales that can be removed without ripping the skin to be eligible, even in theory, to be kosher certified. That includes bass, carp, cod, flounder, halibut, herring, mackerel, trout and salmon, among others, and leaves out catfish, shark and all shellfish. OU Kosher requires that certified manufacturing facilities receive all fish with skin-on (to prevent species substitution) or with a kosher supervision with which we have reciprocity. There are times when a plant will process kosher and non-kosher fish in the same building, and there are conditions under which we can accomplish kosher certification even if all fish handled in the plant aren’t kosher. 

Still have questions?

Question: Our factory cuts multiple species of finfishes, and it also warehouses frozen shrimp (a shellfish that isn’t kosher). Is it still possible to become OU certified?

OU: In many cases, yes. Assuming the shellfish is handled in a way that doesn’t affect kosher production (as determined by OU Kosher), we can allow it. The onsite rabbinic field representative will need to review policies for where and how non-kosher species are handled, which will then be reviewed by the committee in our corporate office. 

Question: We sometimes receive our fish headed and gutted, fileted or otherwise not whole. Is that an issue for OU kosher?

 OU: Depending on where and how it is processed, we can often allow semi-processed fish to be used in kosher production, even if the primary processor isn’t OU-certified. So long as the fish is received skin-on, we would primarily be confirming it is handled by a processor that isn’t switching between species. Fish cut in a local store, where the proprietor cuts an order for single customers, and often doesn’t clean the equipment thoroughly between species, is a concern. A floating processing vessel or fish farm that is dedicated to a single species would be less of a concern for us.

Question: Why is the field rabbi asking about what other species we handle? We’re only interested in getting a single species certified?

 OU: Whether or not OU Kosher can certify your products without requiring on-site supervision depends on an exhaustive review of everything that happens in the plant. Even if “occasionally” you handle a certain species (even if it isn’t intended for kosher), this can affect the status of the equipment and whether we can be sure that there is no accidental species substitution from an approved to an unapproved species.


Question: Our plant wants to bring in tuna loins from a kosher processor to serve a potential OU private label. We also use skinless loins for other customers that don’t require kosher. Is that a concern?

 OU: It is, because it would be difficult to verify exactly which fish was used in which production. In addition, OU kosher views skinless tuna loins as non-kosher, unless they originate from an OU facility, and are sealed in accordance with OU policy. In effect, your plant would be handling non-kosher fish, and we’d need to address that accordingly.


Question: Our plant cuts various species of fish, and many arrive skinless and without kosher supervision. Is there a way we can make a kosher production for a customer?

 OU: OU Kosher can work with you on a variety of potential solutions, including having a rabbinic field supervisor present during kosher production to seal kosher products and assure that it meets OU requirements. In some cases, the plant may only handle non-kosher on a limited basis, and OU would set up a reverse kosher supervision (the rabbi would be present during non-kosher production, to make sure the areas and way that the fish is handled limits the need to kosherize. He would then supervise the cleaning and kosherization of the equipment, and return the plant to kosher status.


Question: Our company does custom processing in a facility that also handles port products, but those belong to the landlord and not our company. Is that a concern?

 OU: The presence of non-kosher products of any type in a plant is something that we look at very carefully. The compatibility of the non-kosher with the kosher production, possibility of cross-contamination or use of non-kosher equipment for kosher are all concerns that need to be reviewed. It is not an automatic deal-breaker.


Question: Is it fair to say that there isn’t a reason to give up our hopes of becoming OU certified simply because we handle possibly concerning ingredients?

 OU: The professionals at OU Kosher have hundreds of years of combined experience in providing kosher certification to manufacturers of all types, with all sorts of concerns. We are happy to work with you on a solution that is mutually acceptable. 

If you have other questions you can contact Rabbi Chaim Goldberg

Rabbi Chaim Goldberg
Rabbi Chaim Goldberg began working at OU Kosher in 2002.  His talents cast a wide net across many areas of kosher certification, with a specialty in the ocean’s kosher bounty.  In addition to supervising many OU-certified fish manufacturing accounts, Rabbi Goldberg has completed hundreds of inspections at manufacturing plants on five continents.  He stores his passport in Brooklyn, NY.