Alert!!! How To Tell Your Sushi is Fresh

I came across this site via Lifehacker.com:

Freshwater fish is riskier than saltwater fish, and salmon is thought to be particularly risky: It can be infected with tapeworms in addition to freshwater trematode parasites. Raw salmon is sometimes brined and vinegared when served raw, but this does not adequately kill any parasites.

Kind of common knowledge, but I thought it was still an informative article.
I love sushi.

How To Tell Your Sushi if Fresh