That's sort of correct. Sushi today is very different than what Japanese people ate hundreds of years ago. Before refrigeration, fish was largely salted or vine

That's sort of correct. Sushi today is very different than what Japanese people ate hundreds of years ago. Before refrigeration, fish was largely salted or vinegared unless it was eaten fresh. Japanese never ate salmon sushi because Japanese salmon often had worms. It wasn't until Norway began importing salmon that Japanese began eating raw salmon. That was a long/difficult road as I heard from Norwegians who know that story. But now Japan imports a lot of salmon from Norway. Also before the modern era, tuna/maguro was not the revered fish it is today. White meat fish were, and to many sushi chefs, still is the top fish for sushi.