Yes, mackerel is kosher. Atlantic, Pacific, Spanish, and king mackerel all have the fins and removable scales that Torah law requires. The Orthodox Union and the Chicago Rabbinical Council both list mackerel as kosher. Canned or smoked mackerel needs a hechsher.

For a whole fresh fish with visible scales, no hechsher is required. The scales identify the species, and that’s your verification. For fillets, smoked fish, canned tuna, or any processed fish, you need a kosher certification symbol. Here’s the complete rule.

Yes, halibut is kosher. It has fins and removable scales, the Torah’s test in Leviticus 11:9-12, and the OU and cRc both list it kosher.

No, shark is not kosher. It has fins but no valid scales, because its tooth-like denticles cannot be removed without tearing the skin. Here is what the OU and cRc say, plus the market names that hide shark.

Can you eat fish and meat together? Not in one dish. Jewish law keeps fish and meat apart for health, though you can have both at one meal with a rinse.

Is caviar kosher? Traditional sturgeon caviar is not, but salmon roe and other kosher fish roe are kosher when certified. Here is how to tell.

Is sturgeon kosher? No. Its embedded ganoid scales can’t be removed without tearing the skin, so the OU, cRc, and Star-K all rule it out.

A kosher symbol, or hechsher, is a certifying agency’s trademark showing a food meets Jewish law. Here’s what the OU, OK, Star-K, Kof-K, and cRc mean, what the D, DE, P, and pareve codes tell you, and why a plain K is not the same.