Besides shellfish, which are some common non-kosher fish to be aware of?
Catfish – (family Ictaluridae) lack scales entirely.20 Interesting for the kosher consumer to note, non-kosher catfish is reported to have a similar taste to the increasingly popular (and kosher variety of) tilapia.21 Catfish and tilapia fillets look almost identical, though catfish is notably cheaper. It is quite possible that an unscrupulous fish retailer might switch the two.