Jewish Law
Kosher Fish Guide: How to Avoid Parasites and Choose Fish With Reliable Supervision
Which fish are truly kosher, which species pose parasite risks, and how to identify trusted certification
- Rabbi Shai Amar
- |Updated
There was a time when buying fish was simple. You’d go to the local market, choose your fish for Shabbat or the holidays, and just make sure it had the kosher signs of fins and scales.
Today, things have become far more complicated. Due to the discovery of parasites and worms that sometimes appear in the flesh or organs of kosher fish, consumers must now be familiar with the basic halachic laws of fish inspection, to avoid eating forbidden creatures.
This guide provides a clear overview of what to look for when buying fish — for Passover and throughout the year.
A Problem Discussed for Centuries
The issue of worms found inside fish is not new. It was already discussed by halachic authorities hundreds of years ago.
The Beit Lechem Yehuda (Yoreh De’ah 84:37) warned: “One should be careful to cut away the gills, for it is very common to find there very small worms.”
Similarly, the Orach Mishor wrote: “Care must be taken, for this is frequent. I have seen many times in certain fish that small hair-like worms move about near the head — and there is no doubt they come from outside the fish. This is therefore a Torah-level prohibition.”
(Photo: shutterstock)How Fish Are Sold Today
Fish now reach consumers in two main ways:
Fresh, open display — at local fish shops.
Sealed packaging — in supermarkets or frozen sections.
Different kashrut organizations handle the issue of parasites in fish differently. Here’s what you should know:
1. Fish Sold Under Local Rabbinic Supervision
Before buying, ask the mashgiach (kosher supervisor) whether there is inspection for worms and parasites.
Farm-raised fish, such as tilapia (amnon), silver carp (kasif), bass, white bass, buri (mullet), barramundi, amur, and carp — are generally free from concern, since they grow in treated pools.
However, sea fish and imported frozen fish may present a high risk of parasites, and require closer inspection.
2. “Mehadrin” Supervision (Strict Kosher)
Farm-raised fish under mehadrin supervision are safe, as they come from controlled environments.
Sea fish and imported frozen fish, however, are problematic. Even with mehadrin certification, if they are unpackaged, the supervision cannot prevent internal parasites, since these worms are often found inside the fish’s flesh or abdominal cavity.
If, however, the fish arrives in a sealed package bearing the name of a recognized and reputable Badatz (kosher authority) stating clearly that it is free of parasites, the fish may be eaten without concern — even by the strictest standards.
3. Be Careful: Fish With Known Parasite Issues
Some fish species are known to have a high rate of parasite infestation, even within the flesh itself. Among them:
Pollock
Salmon (except those imported from Norway and Chile)
Sole (except those imported from the Netherlands)
Because of these issues, some of the strictest kosher organizations refuse to certify certain varieties of these fish altogether.
4. Fish That Require Parasite Removal Procedures
Some fish, like redfish and hake, may be used only after special inspection and removal of parasites.
(Photo: shutterstock)How to Remove Parasites From Fish
When cleaning or checking fish yourself, follow these steps:
After removing internal organs, carefully check that no small pockets or sacs remain inside the abdominal cavity.
Probe 1.5 cm (½ inch) into the flesh to locate and remove any anchored parasites, which often attach deep within the muscle tissue.
This meticulous checking process is essential for certain species known to be at risk.
Kosher Fish in the Modern Marketplace
Always confirm supervision details and species source before buying.
Farm-raised fish in treated ponds are generally safe.
Wild-caught or imported frozen fish need special attention — and ideally, mehadrin certification from a reputable kosher authority.
When in doubt, consult a qualified rabbi or kashrut expert before purchase.
By being informed and careful, you can enjoy your Shabbat and holiday fish dishes — with full confidence in their kashrut.
