Buying Fish

Can I buy a kosher fish species from any fishmonger, even one that sells non-kosher seafood? Do I have to bring my own filet knife and ask him to use it, or can I just watch the fish being cleaned and butterflied (for example)?

Shalom!

Thank you for your question.

It is permitted to purchase cut fish in a non-kosher store, such as the community supermarket, as long as a number of precautions are taken.

A fish is kosher as long as it has fins and scales. It is worth mentioning the “scales” do not include all scales. Rather, “scales” are defined as scales that can be removed without damaging the flesh of the skin. There are a number of non-Kosher fish that have scales, but they are so embedded in the skin, that the skin is damaged when removing them.

One must be sure to see the fins and scales on the fish in the supermarket that one wishes to purchase.  When the fish has been cut in the supermarket, there are concerns as to which knives were used to cut it. The knives may be interchanged for use with non-kosher fish and thereby have non-kosher residue on them.  As such, one should ideally bring a cutting board and knife to the store, but if need be, one may simply ask the fish salesman to clean the knife and work on a clean surface when he is cutting up your fish. If even this is not possible, one may still purchase the fish, but it should be washed well under running water while wiping it. It may then be used.

Finally, one additional concern to be aware of is that some wild-caught fish are infested with the anisakis worms and should be avoided. Norwegian salmon is usually free of this problem, but one must be alert, and check the origin of the fish.

Avoda Zara 39; YD 118:1; Pitchei Teshuva, YD 96:5.