If everyone followed that rule . . .
. . nobody would be eating fish - they'd be extinct or near extinction and priced so high they'd all be shipped to Japan (where high price is considered the greatest flavor enhancement).
U.S. rainbow trout production in 2002 was over 27,000 tons (and the U.S. is not the largest producer). Salmon production was over 14,000 tons and catfish production was over 315,000 tons. There is no chance in hell this volume could be produced by "wild catch".
Fish farming definitely presents environmental and health problems, but those problems need to be worked out. A lot of progress is being made.
As for Southeast Asian fish (farmed and wild caught), producers are increasingly US FDA [link|http://www.cfsan.fda.gov/~lrd/haccp.html|HACCP compliant] (Hazard Analysis and Critical Control Point), particularly in Vietnam.
It is not difficult for small markets to obtain properly certified products from wholesalers.
A couple of years ago U.S. catfish farmers, concerned by imports of Vietnamese catfish (basa and tra), sent an expedition to gather information about the Vietnamese catfish industry, hoping to use it in marketing.
One representative stated, "We went to Vietnam expecting to find fish grown in poluted water and processed in primitive facilities. That is not what we found and we're scared to death."
Incidentally, Vietnamese catfish is not like American channel cat. It's from a genus called "shark catfish" due to their shape. Fillets are thinner and broader and the flavor is less assertively "catfishy". Very good fish, all in all.
[link|http://www.aaxnet.com|AAx]