I've been to many sushi places and last night I went to a place that I've been to before (not that long ago either). When the sushi came, we noticed that it had wasabi spread on the rice, under the fish.
When we complained we were rudely told that the chef had been doing sushi for 30 years and wasabi is used to kill parasites in the fish.
This is believable since I know in some countries, red peppers are used in foods all the time for the same reason.
However, my understanding of sushi is that the chef is a craftsman who not only picks great fish, but also knows how to find and remove parasites.
My question is, is this normal? Is it proper for the Sushi chef to add wasabi to the sushi to help prevent parasites? If so, how come I've only encountered this practice once out of the many sushi places I've frequented?