Michigan's fishery officials faced a challenging decision this week as they were forced to euthanize over 31,000 Atlantic salmon due to an outbreak of bacterial kidney disease (BKD). The illness was discovered during a routine prestocking inspection at the Harrietta State Fish Hatchery in Wexford County. Michigan State University's Aquatic Animal Health Lab confirmed the presence of Renibacterium salmoninarum, the bacterium that causes BKD, as reported by Michigan Department of Natural Resources.
Despite efforts to recover the fish, including a 28-day antibiotic treatment completed May 17, the infection was not fully eradicated. "These fish were sick enough that a significant portion of the fish were not feeding well," Aaron Switzer, DNR Fish Production Program manager, said. This resulted in an inadequate intake of the medicated food necessary to eliminate the pathogen. The infected fish, still showcasing signs of active disease, were deemed unsuitable for stocking and therefore had to be quickly and humanely disposed of.
According to CBS News Detroit, Assistant Chief Ed Eisch of the DNR Fisheries Division expressed the weight of the decision, stating, "Having to make the decision to dispose of these diseased fish hurt, but it was clearly the right thing to do." The fish were euthanized using carbon dioxide and then buried in a pit to prevent any spread of the infection to other aquatic life in Michigan's public waters. The atlantic salmon, a species highly valued for recreational fishing, necessitate careful management to uphold the public trust responsibility to Michigan's aquatic ecosystems.
While the loss of the infected fish is significant, Michigan's Department of Natural Resources ensured that other hatcheries are continuing to stock healthy fish. Eisch informed that the fish from the Platte River State Fish Hatchery were confirmed healthy and released into several locations, including Torch Lake, the Au Sable River, the Thunder Bay River, and Lexington Harbor on Lake Huron. The St. Marys River received nearly 27,000 fish this week as part of the DNR's initiative, which continues to annually stock between 20 to 30 million fish across the state's waters. Moreover, efforts are being made to better secure hatchery infrastructure against future outbreaks, aiming to enhance the biosecurity measures in place.
As a silver lining to the situation, scientists at Michigan State University are in the process of developing a vaccine to protect the fish populations from future outbreaks of BKD. This proactive approach might help to arrest the spread of such diseases before they can cause harm to michigan’s valuable aquaculture industry.
