Kosher fish have fins and scales.
I've attached a related link that provides a comprehensive list of kosher fish.
Yes opa is a kosher fish. Any fish that is born with scales and a dorsal fin is kosher. As long as it hasn't been touched by a non kosher knife
Sharks, rays, eels, and catfish are all good examples of fish (in the traditional sense) that are non-kosher.
Rascasse fish is also known as Scorpionfish which is a kosher species. Please see the related link for a comprehensive list of kosher and non-kosher fish.
If it comes from kosher fish such as whitefish, yes. If it comes from non-kosher species such as sturgeon, then no.
Yes, carp is kosher. For a list of kosher/non-kosher fish, please see Related Links:
No, monk fish has been determined to be non-kosher.
Yes, religiously observant Jews can purchase fish from a store that sells non-kosher food. However, the fish in question must have its skin on. If it doesn't have its skin on, it must be in a sealed package that is labelled kosher by a reliable hechsher.
No.
Fish and chips can be kosher if it`s made with kosher fish in a kosher kitchen. In fact, it was Portuguese Jews who introduced fried fish to England.
Fish and chips can be kosher so long as the fish used is a kosher species and the food is prepared in a kosher kitchen with all kosher ingredients.
The signs of a kosher fish are scales and fins. If the fish does not have either of these, then it is not a kosher fish. If it does, it is a kosher fish and one may eat it provided, of course, that it was prepared with kosher ingredients. According to "kashrut.com" (see link in related link section), the Grouper is indeed a kosher fish.
Clownfish, also called anemone fish, are a type of Amphiprioninae, of the family Pomacentridae. They are not included on any list of kosher or non-kosher fish. Because they have fins and ctenoid scales, they are presumablykosher. However, this answer should not be taken as a certification of kosher-status: a more knowledgeable source should be sought.