I am new to exploring the fun world of home-made sushi, and have recently started branching out to include raw fish. I just picked up a wild copper river salmon fillet from the market, but now that I'm doing some online reading, I see that apparently it is not a good idea to use wild salmon for sashimi. Is this true? Would it be better if I purchased farm-raised instead? It isn't labeled as 'sashimi grade' . Would it be better if I froze it overnight, or should I just give up and put it to another use?