Michigan kills 31,000 Atlantic salmon after they catch bacterial kidney disease at hatchery
More than 31,000 Atlantic salmon raised in a Michigan fish hatchery had to be killed after failing to recover from disease, officials said Tuesday.
The decision followed an unsuccessful 28-day treatment period at the Harrietta hatchery in Wexford County in northwest Michigan.
"Having to make the decision to dispose of these diseased fish hurt, but it was clearly the right thing to do," said DNR Fisheries Division Assistant Chief Ed Eisch in a statement. "The Atlantic salmon fishery is highly valued, but first and foremost, we have a public trust responsibility to protect the aquatic resources of the state of Michigan. Stocking fish known to be actively suffering a disease outbreak would be counter to that."
The fish, around 6 inches long, were loaded into a truck Monday, euthanized with carbon dioxide and buried in a pit, Eisch said.
The salmon, sick with a bacterial kidney disease, were treated with medicated feed.
"The bacteria that causes bacterial kidney disease is listed as a Level 1 restricted pathogen in the Model Program for Fish Health Management in the Great Lakes," said Eisch. "Fish that are positive for Level 1 restricted pathogens can be stocked where the pathogen is already known to exist, but only if they are free of signs of disease. This lot of fish still shows signs of active BKD so they cannot be stocked."The unhealthy fish would have posed a risk to other fish if they had been released into Michigan waters, he said.
The disease likely came from brown trout at the hatchery.
"We think there some latent bacteria in the brown trout, and they were releasing the bacteria, enough that the Atlantics picked it up and got sick from it," Eisch said.
Officials say BKD causes death in salmon and trout and is believed to have played a large role in the decline of Great Lakes Chinook salmon populations in the mid-1980s.
The DNR says it stocks 20 to 30 million fish each year in Michigan's public waters. Healthy Atlantic salmon from Platte River State Fish Hatchery were stocked in Torch Lake, the Au Sable and Thunder Bay rivers, and Lexington Harbor in Lake Huron. The St. Marys River in Sault Ste. Marie also received nearly 27,000 fish this week.
Scientists at Michigan State University plan to try to develop a vaccine to protect fish from future outbreaks, Eisch said.