I stand corrected...after opening my textbooks and doing some online research I see now why Sushi should come from as deep water as possible, and not fresh water fish, because the high levels of tape worm. And other parasites. I have eaten raw fish, of many different kinds, as it is part of my job to inspect the quality of food all the time, even though that can lead to being sick. But with the exception of frozen at sea fish destined for Sushi or Sashimi, I normally leave the Sushi making to the experts, and now I see why.

I was watching an episode of 3 Hungry Boys the other day, where they ate Pollack they had caught just off the shore as a Sushi.
I saw Gordon Ramsey or Jamie Oliver make Sushi from freshwater fish, and Sushi is real trendy these days, so it seems natural to folks that it must solely be based on freshness and diversity in preparation. But in fact, fresh water fish like Heck/Pike have something like 30% percent and more chances of carrying tape worm.
I am including a link I found that explains it best, and is factually correct, as far as I can tell.

http://vitalchoice.com/uploads/Sushi%20Safe.pdf

Just a counterpoint to all the fairly opinionated and not-that-informed posts so far:
- Sushi is expensive wherever you are. I live at the sea in a country full of cheap restaurants now and good Sushi costs not much less than in Europe. You CAN get cheap stuff, but while I am a cheapskate with all other types of food... I only buy sushi at the most trustworthy places. Because raw fish is simply a sensitive ingredient.
- Swiss restaurants are expensive cause the labour costs and some ingredients are. For example beef. Sushi does not require many expensive Swiss ingredients and good quality imported fish is not more expensive than good cuts of beef. I spend less in a Sushi restaurant than in a steakhouse.
- making sushi yourself is really not that difficult. Getting fresh fish for it isn't hard either. My favourite place is this chain usually hidden in the industrial areas. They dont just sell tuna and have the best filets already cut in sushi size. http://www.der-frisch-fisch.ch/site/...TO___Der_e.cfm
- It is not the most original stuff, but I actually very much like Yoojis. By now a chain as well with outlets all over Zurich. http://www.yoojis.ch/

I've driven past the Mercato in Dietlikon and am anxious to try it. Good to know. I've taken a sushi making course but am an uncoordinated ditz with rolling. My sushi rice is good though.

We went to the yoogis in Winterthur and found it quite ok...the fish all seemed to be fresh, the sushi was tasty. For us, very convenient.

So freeze it first, problem solved!

Also, Sushi is not always raw, nor does it always contain fish, BUT, it does always contain rice.

Tom