Disease in Atlantic salmon caused by a virus, spread easily in crowded fish farm conditions in both Pacific coast and Atlantic coast farms.

How to tell if your salmon has ISA:

  1. Your salmon may be lethargic.
  2. Check your salmon for interior lesions, including hemorrhaging on the kidney and other organs.
  3. Does your salmon have swollen eyes?
  4. Fluid in the body cavity?
  5. Pale gills?
  6. Swollen kidneys or spleen?
  7. Check for darkening of the posterior gut.
How did your salmon contract ISA?
Your fish probably came in contact with an infected fish; or in contact with mucus, blood, viscera, trimmings, muscle, or feces of an infected fish; or in contact with equipment contaminated with parts from an infected fish; or contact with people who handled infected fish, fish parts, contaminated equipment or were on, in, or around ISA affected sites. The virus doesn't cause disease in people, but they can carry it.
So can sea run brown trout and rainbow trout.
And so can sea lice.

Oh, and if your farm is within 5 km from an infected farm or processing plant handling infected fish without adequate waste treatment, your salmon are at a 5-13 times higher risk of getting ISA.

ISA first gained attention when it swept through the Norwegian fish farming industry in 1984, which set up quarantine zones. Scotland and the Shetland islands caught it next, and implemented a compulsory slaughter regime for infected farms, followed by a fallow period. In 1996, it hit Canada's Atlantic fisheries. In 1998, the Canadian government paid New Brunswick fish farmers more than $6 million to kill one-third of the province’s total production in an effort to stop the spread of the virus. That didn't work. Next, Canadian aquaculturists in New Brunswick began vaccinating smolts with an autogenous vaccine in the winter of 1998, and have chosen to vaccinate the fish in their 1999 year class smolts. That didn't eradicate it either, and every Canadian farm tests their fish now. US salmon farms in Cobscook Bay are close enough to fall within the ISA virus positive "quarantine zones" in New Brunswick waters, the question of when ISA reaches Maine is not "if" or "how" but "when."

And one more thing: In October 1999, it was confirmed that infected salmon had escaped and spread the disease to wild populations. Next to genetic dilution, disease poses the greatest threat to the survival of wild Atlantic salmon.