This is what you may eat of all that is in the water: You may eat any creature that lives in the water, whether in seas or rivers, that has fins and scales. (Leviticus 11:9) There is a tradition from the Baal Shem Tov not to eat a type of fish called a tench,¹⁶ as there is a concern that it falls under the category of “a swarming thing that swarms on the earth” (ibid. 11:41).¹⁷ Darchei Teshuva #83:7, in the name of the Imrei Sheifer

footnotes: ¹⁶ Or “gypsy fish” (Tinca tinca). A freshwater game fish of Europe and western Asia noted for its ability to survive outside of water. ¹⁷ Even though this fish has fins and scales, the signs of a kosher species, its ability to survive on the ground may put into the category of forbidden crawling creatures.