Remember, there are two parts to Kosher. One is that the fish itself is acceptably under kashrut. The other is that it is prepared under kashrut. The fish is not going to be kosher if the restaurant cuts it up with the same knives used to cut up the shrimp and octopus.
Pacu (not paco) fish seems to be a somewhat uncommon type in the Jewish community from what I've seen. When in doubt, ask a Rabbi! I've never met a Rabbi that didn't like to ask questions about Judaism.
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.
Kosher fish have fins and scales. I've attached a related link that provides a comprehensive list of kosher fish.
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.
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
Basa fish, just like all other forms of catfish, is not kosher.
Sawfish, also know as Carpenter Shark, are a family of rays. These fish are not kosher as they do not meet the two requirements of kosher fish: movable fins and easily removed scales.
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.
Brazino, also known as seabass, is a kosher species of fish.
Seer fish, also known as Spanish mackerel, is kosher.
No. Swai is a type of catfish, and catfish are not a kosher species of fish.