This time of year is about the worst time of year for fish in Iowa’s lakes and ponds, according to a state fish expert. Joe Larscheid, a biologist at the Spirit Lake fish hatchery, says it’s called summer stress.Low water levels and the heat of late summer often combine to reduce oxygen supplies and kill fish. Larscheid says wildlife staff and farmers are virtually powerless to stop the summer stress kills from wiping out big populations of fish in the endangered ponds.But he says even heavy rains can hurt the situation. Storms may raise the lake levels while increasing the amount of nutrients being washed into the water, making the situation worse. Larscheid says another bigger concern than the summer stress is coming in a few months, with winter kills.Depleted oxygen supplies resulted in fish kills last week at: Lost Island Lake in Palo Alto County, a private pond in Polk County and several farm ponds in Warren County.
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