Bauer said a single dry year usually isn't enough to hurt the fish population. But he worries dry conditions in Nebraska could continue, repeating a stretch in the mid-2000s that weakened fish populations.
Kansas also has seen declining water levels that pulled younger, smaller game fish away from the vegetation-rich shore lines and forced them to cluster, making them easier targets for predators, said fisheries chief Doug Nygren of the Department of Wildlife, Parks and Tourism.
Nygren said he expects a drop in adult walleye populations in the state's shallower, wind-swept lakes in southern Kansas. But he said other species, such as large-mouth bass, can tolerate the heat and may multiply faster without competition from walleye.
"These last two years are the hottest we've ever seen," Nygren said. "That really can play a role in changing populations, shifting it in favor of some species over others. The walleye won't benefit from these high-water temperatures, but other species that are more tolerant may take advantage of their declining population."
Geno Adams, a fisheries program administrator in South Dakota, said there have been reports of isolated fish kills in its manmade lakes on the Missouri River and others in the eastern part of the state. But it's unclear how much of a role the heat played in the deaths.
One large batch of carp at Lewis and Clark Lake in the state's southeast corner had lesions, a sign they were suffering from a bacterial infection. Adams said the fish are more prone to sickness with low water levels and extreme heat. But he added that other fish habitat have seen a record number this year thanks to the 2011 floods.
"When we're in a drought, there's a struggle for water and it's going in all different directions," Adams said. "Keeping it in the reservoir for recreational fisheries is not at the top of the priority list."
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