BANGOR – A lone salmon suspected of carrying a deadly disease that could have threatened efforts to restore endangered wild Atlantic salmon to several Maine waterways has tested negative for the infectious salmon anemia virus, the U.S. Fish and Wildlife Service said Friday.

But the salmon – nicknamed “the bad boy” – will remain alone in a separate tank at Craig Brook National Fish Hatchery in Orland while additional genetic and disease tests are conducted.

“It’s part of our precautionary approach,” said Jaime Geiger, assistant Northeast regional director for fisheries at the U.S. Fish and Wildlife Service in Massachusetts. “We’re trying to get a genetic analysis of the fish … to see where it came from.”

“Bad boy” was caught in a trap in the Penobscot River in Veazie for use as brood stock at the fishery. Initial blood tests, which have been known to give false positive results, showed the salmon had the deadly disease.

Infectious salmon anemia virus has been causing millions of dollars in damage to aquaculture operations in New Brunswick and has been confirmed in commercial sea pen facilities in Maine. The disease can cause death in salmon in saltwater, but fishery biologists do not know what effect it will have on fish in freshwater. The virus poses no danger to humans, officials say.

This year, 42 of the 85 wild salmon pulled from the Penobscot River have undergone the initial blood test. “Bad boy” was the only one to test positive. Because of that, the Fish and Wildlife Service began a 28-day cell-culture test, considered the best science available to confirm the presence of the disease.

Geiger said that even though the Fish and Wildlife Service no longer considers “bad boy” a threat, the fish remains the icon of what could have been the halt of Atlantic salmon restoration programs. The disease was one of the reasons the federal government designated Maine Atlantic salmon as an endangered species.

“Bad boy” is a male fish that was raised in a hatchery and spent two winters in the ocean before returning to Maine.

“Given the seriousness of ISAv, we don’t want to take anything for granted,” Geiger said. “In one sense, we have dodged the silver bullet here.”

What the Fish and Wildlife Service hopes to find out through the additional round of tests on “bad boy” is not known, but Geiger said he believes there probably will be nothing.

“I’m making no assumptions that anything’s wrong with this fish,” he said.

“Bad boy” and other salmon at Craig Brook will be retested this fall, Geiger said, before they are allowed to produce offspring.

The Fish and Wildlife Service is conducting genetic testing on the salmon at Craig Brook as part of a comprehensive genetic management plan.

“We will have a genetic fingerprint of each one of these fish,” Geiger said.

After the fish spawn, the Fish and Wildlife Service should be able to predict the genetic makeup of each fry, or minnow-size salmon, Geiger said.

So far this spring, 171 salmon returning from the ocean have been caught in the Veazie trap and 143 were taken to Craig Brook to be used as brood stock. In a separate area of the hatchery, six populations of fish considered endangered species are being held to minimize disease contamination from other populations.

Last year, these fish produced hundreds of thousands of fry that were released into the Dennys, East Machias, Machias, Narraguagus and Pleasant rivers in Washington County and the Sheepscot River in Lincoln County.