Sushi is very good and very tasty if its smells fishy or taste fishy it is not good sushi. As fowlmood said the word stands for the type of rice used and the way it is prepared. you can stick a corn dog in the wrap of nori and rice and it would be a sushi roll. sushi its self is the pad of rice with a topping could be raw fish or other items. However you should never use fresh water fish the impurities in the water are in the fish whether it be parasites high mercury or so on. if you insist on using fresh water fish please cook it throughly smoking is fine whether it can be cold or hot smoke. even maybe a crappie tempura that would be interesting.