PIERRE, S.D. – Game, Fish and Parks officials say bacteria are responsible for Lake Oahe’s white bass deaths.
Results from a diagnostic laboratory confirmed that the Flavobacterium columnare bacteria, commonly referred to as columnaris, are to blame for the recent white bass die-off on Lake Oahe. Game, Fish and Parks Fisheries Biologist Robert Hanten of Pierre said warm water temperatures that are common this time of year create stressful conditions for white bass and make them more susceptible to this common microorganism.
"White bass die-offs are unfortunate and unsightly, but not uncommon," he said. "Other states have experienced similar fish die-offs that were due to out-breaks of columnaris bacteria, which were also associated with warm water temperatures."
Columnaris bacteria affects the gill filaments of fish, and a schooling species of fish, like white bass, are especially susceptible. "The bacteria attach to the gill surface, grow in spreading patches and eventually cover the gill filaments," Hanten noted. "Skin lesions may also be noted on the body and inside the fish's mouth. The end result of a heavy infection is mortality."
Bacteria, such as columnaris, are found in all natural waters and do not affect healthy fish. However, when fish become stressed, they are much more susceptible to diseases. Fish can experience stress due to many things, such as warm water temperatures, injuries, limited food and spawning.
"White bass die-offs of large magnitude do have an impact on the overall white bass population, but white bass populations are very resilient and they reproduce in high numbers," Hanten said. "The high reproductive potential of white bass allows for them to recover quickly from die-offs like the one that is occurring on Lake Oahe."
Anglers and other water enthusiasts have two main concerns with this occurrence. Is there any danger to game fish populations and is there any danger to humans?
"This fish die-off has been limited to just white bass, and no other game fish have been effected," Hanten said. "At this time, we feel that the columnaris bacteria pose no risk to humans. The die-off will run its course and things will return to normal on the big lake."
Fish sent off to diagnostic laboratory were also tested for the anthrax bacteria, and as expected, came back negative for the bacteria. Anthrax is soil-based and only infects mammals, typically grazing herbivores such as sheep, cattle and goats and does not infect amphibians, reptiles or fish.