Check out the last three paragraphs of this article http://www.gofishbc.com/tips_articles/stillwater.htm Chef's advice in a recent post about buttermilk seems to hold some merit based on some related articles I found. Commercial fish farms transfer the fish from rearing ponds to clear moving water for a few days before slaughter. If this is not practical, there are suggestions to soak the fish in milk/buttermilk in the fridge for a few hours. Apparently, this draws the taste from the skin and the underlying fatty layer of the fish were the taste is contained. The milk should not be retained for cooking.