I went to Blue Ribbon sushi last night and the quality of my sushi/sashimi had markedly deteriorated. Salmon was gristly, chewy, slightly fishy, and almost inedible. Spanish mackerel was tasteless and similarly chewy. My question is about sushi preparation....at the finer sushi places like Sushi Yasuda, the fish just seems to melt in your mouth and there is no "chewiness" or gristle involved. How does a good sushi chef achieve what was sorely lacking at Blue Ribbon? Is there a certain cutting technique or is it the fish itself?