Nature Lab

Fisheries Management

Watching for Pathogens at Fish Hatcheries

Each year MDC stocks an average of 4.6 million fish of various species in rivers and lakes across the state. To be released into the wild, these hatchery-raised fish must be healthy.

“We want to be good stewards of the resource and not perpetuate any diseases or introduce any new pathogens into Missouri’s waters,” explains MDC Aquatic Animal Health Specialist Larry Durham.

MDC’s nine hatcheries all follow best management practices. Most fish stay healthy, but when they don’t, staff have protocols for detecting pathogens (bacteria, viruses, and parasites). Hatchery staff watch the behavior, appearance, and eating patterns of the fish. If something looks off, they call Durham.

“I check the fish for any abnormalities in their organs or on the skin, gills, or eyes,” says Durham. “I look mainly for bacteria or parasites because those are the things we can treat. If we suspect a virus, samples are sent to a federal lab for testing.”

Often fish can be treated with medicated food or by adding treatments to the water to kill bacteria and parasites. If an outbreak isn’t treatable and is causing major loss, the fish may be euthanized, and the rearing units are disinfected.

In addition to diagnosing and treating infections, Durham and staff conduct inspections. Twice a year, 175 fish are sampled from each trout hatchery and tested for specific fish pathogens.

“By keeping records of when and where pathogens occur, we can assess hatchery practices to look for where we can improve,” says Durham. “Accurate documentation allows us to see patterns and make better predictions. Hatchery management can then be altered to reduce or eliminate the problem. Ultimately, prevention is key for fish health management.”

Watching for Pathogens at Fish Hatcheries at a Glance

MDC hatcheries are managed to prevent the spread of pathogens (bacteria, viruses, parasites). If hatchery fish die or show signs of being sick, they are checked both externally and internally to determine the cause. After a diagnosis is made, staff treat the fish as fits the situation.