Steve Ellis of USDA and Sharon MacLean study salmon virus 
problem of aquacultured salmon.  When more that 2% of fish 
die per day the whole pen should be killed.  The virus may be 
spread in stun water and processing plant waste and picked up 
and carried by various carriers in the natural population.  
They are sampling the blood of several species around the 
north Gulf of Maine waters that abut the salmon aquaculture 
pens.