Connecticut River Wild Atlantic Salmon Destroyed
After European Virus Detected
by Fishermen'sVoice staff

Healthy wild Atlantic Salmon are kept at the salmon station where they continue to spawn. Holding tanks for the infected fish had to be disinfected. Salmon adjust their skin color to match the bottom for camoflage. The black salmon in the photo, is blind, thinks its surroundings are black and changed its color accordingly. Fishermen’s Voice photo

All 140 of the Atlantic salmon that returned to the Connecticut River in 2007 were destroyed after a routine test detected a virus in October. The virus, infectious pancreatic necrosis, known to be naturally occurring in some New England trout, is contagious and deadly for Atlantic salmon. The virus is not a threat to humans, but is deadly for salmon and can rapidly devastate salmon in pens at aquaculture facilities.

The virus only spreads when the eggs hatch. It then expands rapidly and the tiny fish that hatch from infected eggs hemorrhage and die. As a precaution the Sunderland facility destroyed approximately 8,000 eggs from each of the spawning salmon, an estimated 718,000 eggs in all. Of the 2007 run of salmon returning to spawn in the Connecticut River watershed, two samples from the100 fish tested were positive for the virus.

The fish were captured by the staff of the Cronin National Salmon Station in Sunderland, Massachusetts. This federal facility, part of the Atlantic Salmon Restoration Project, is the only one in the Connecticut River watershed, which collects sea run Atlantic salmon returning to spawn.

Healthy salmon spend two years in the fresh water where they were born, and then at 4” to 8” long they migrate downstream to the ocean. In the process they change physiologically, their liver, kidneys, and blood chemistry transform to function in salt water. From New England rivers, they head north to the Arctic Circle where they feed on capelin, a small fish.

After two years in the Arctic they swim back south until they recognize the scent of the river they left two years earlier. Weighing an average of 10 lbs., they swim up to the headwaters of their river of birth.

Atlantic salmon have been extinct in the Connecticut River since the 1700’s when dams were built on it and many of its tributaries. At one time 880 dams blocked passage of the once enormously plentiful fish. There are still 800 dams in the Connecticut River watershed, one of New England’s largest rivers. Now they travel as far upstream as fish ladders or the restoration project allow.

Every year the Cronin salmon station catches returning salmon, collects the eggs, collects sperm from males, artificially inseminates the eggs and hatches them out. Unlike other salmon, Atlantic salmon do not die after spawning, but spawn for five or six years, and more than once per season. The salmon are tested for viruses, have a tracking chip implanted in them and are kept at the station. The Cronin Station is the only hatchery in the world mating fish using DNA testing to maximize genetic diversity and strength. Once hatched, the small fish, molts, are released into the river.

The hatchery manager, Mickey Novak, said, “We dodged a bullet this year, we nipped it in the bud. There will not be any long term impact.” Other precautions taken were the cleaning and sanitizing of tanks that held the fish and running the water through an ultraviolet system to sanitize it before discharging.

This was the first time the virus was confirmed in North America. The genotype of this particular virus matched a virus common in Atlantic salmon from rivers of Europe, Norway, and Scotland. This finding verified that the wild American Atlantic salmon were mixing with wild European salmon in the feeding grounds they both migrate to at the Arctic Circle near Greenland and Baffin Island.

Wild salmon from European rivers also migrate to the Arctic. On the way they swim through coastal waters where many large northern European aquaculture facilities have millions of salmon penned. It is in the tons of feces that pour from these pens and cover the bottom, that the viruses grow, spread and infect passing fish. Genetic tests of this particular virus suggests Connecticut River salmon picked up the virus while mingling with European salmon.

In November 2007, there were 5.5 million salmon killed by another virus at salmon pens in Chile. Chile produces 35% of the world’s pen-raised salmon. For a decade in the 1990’s, Scotland salmon farms had recurring problems from viruses.

The pressure of bursting world populations needing food, diminished and threatened wild fisheries, and the looming disaster an inadequately planned aquacultural production expansion poses to both, are problems that have to be faced. Which of these problems the U.S. government—from the Department of Commerce to NOAA to NMFS chain of command—decides to focus on first is of concern to scientists and fishermen alike; each who recognizes that such a decision could have broad consequences.