I initially suspected some Celsius-Fahrenheit confusion, but other sources corroborate these temperatures. Color me perplexed.
For what it's worth, I had fish last night. Cooked it 20 minutes at 180C. Was not shrunken or dry. Guess I'm doing it wrong?
In one study it was shown that refrigerated or frozen sushi had less aerobic mesophilic bacteria than freshly prepared sushi, and that the preparation varies between restaurants/chefs. But more people get bacterial infections from produce and rice than from fish.
On the culinary side of things, it can be easy to overcook certain fish, and other fish are much more lenient. Some of the most delicious tasting fish should be served raw or in-between raw and fully cooked. This way both delicate flavors and firm tissues don't break down completely.
For a typical salmon steak, 145C for 20 minutes is about right. The idea is to get it up to temperature, then remove it and cover it and let the residual heat keep cooking the fish for 10 minutes, allowing juices to settle back in (much like other meats). Alternately you can cook at a higher temperature for shorter time and apply a sear after. But in general, once the meat turns opaque all the way through, it's at the perfect state just a couple minutes later.