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Hard Winter Takes Toll on Iowa Fish
DES MOINES - The winter that seemingly wouldn't quit is finally beginning to show signs of weakening as the thick crust of snow and ice covering Iowa lakes, ponds and streams begins its slow retreat. Once the ice is gone, the evidence will be seen in shallow lakes and ponds as fish that died during the hard winter will be found along shore. Winter mortality happens to varying degrees during most years and the 2009 winter will likely have an impact on some Iowa's lakes and farm ponds. Most lakes entered winter with above normal water levels, but the all-of-a-sudden onset of ice, followed by a never-ending parade of snow storms shut out the sunlight, capping the oxygen level in the water. "We have been monitoring a number of shallow lakes and backwaters that have extremely low dissolved oxygen levels and I would expect to see a fair number of winter stress kills after the winter we had," said Joe Larscheid, chief of the DNR's Fisheries Bureau. "It is important to keep in mind that having a winter kill is not the end of the world. It usually only affects a portion of the fish population and the fish that remain will grow quickly." The most recent report of dead fish was in the Pool 15 of the Mississippi River. An unknown number of dead freshwater drum and a few other species were reported to the Iowa Department of Natural Resources who sent the local fisheries biologist and environmental specialist to the scene to investigate. The cause: winter stress from low levels of dissolved oxygen. Carter Lake, which borders Omaha, has seen a die off of channel catfish and carp for the same reason. The DNR has opened Little Clear Lake in Pocahontas County and Pickeral Lake in Buena Vista County to promiscuous fishing from Feb. 22 through March 14, due to severely depleted oxygen levels. The extent of a die off will not be fully known until later this spring or summer, when fisheries biologist can take an in depth look at the population during their annual fish population surveys. "For the most part, we will allow nature to fill in any vacancies, but on the rare occasion if there was a significant die off, then we may take some steps to help the lake recover," Larscheid said. While winter stress kills are natural, the DNR does not want the public to assume every kill is winter stress related and would like to know when three are dead fish in the lakes or streams. "It's nature's way. Fish die during the winter and once the ice goes out, those dead fish will be a major source of food for channel catfish. In the short term, this can be an excellent time to catch really big catfish as they go on a feeding frenzy," he said. "In a few years, fishing can be really good because the remaining fish will grow quickly. "The locals know this and will be there in two years when fishing is really good," Larscheid said.
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