Herald JournalHerald and Journal, July 15, 2002

Large fish kill on Lake Ann adds to lakeshore worries

By Lynda Jensen

Thousands of dead fish washed ashore at Lake Ann during the Fourth of July holiday.

Between 5,000 and 10,000 fish, mainly small perch, were killed from low oxygen levels, said Paul Diedrich of the Department of Natural Resources.

"It was all species ­ all kinds," commented Tom Hammer of the Lake Ann Lake Association.

The low oxygen was likely caused by shallow flood waters that washed into outlying areas, remained standing over dying vegetation, and then washed back into the lake, Diedrich said.

Dying vegetation removes oxygen from water. This oxygen depleted water flowed back into the lake, which likely caused the fish kill when combined with the hot sultry weather, he said.

However, the dead fish are also the result of agricultural waste washed into the lake, Hammer said.

Lake Ann's watershed naturally contains a lot of runoff from local farms, Hammer said. "It's the way our water shed is designed," he said.

When manure is washed into ditches, the ditch water is basically processing waste, and depleting oxygen in the water, he said.

Hammer pointed to a fecal coliform sample taken from County Ditch 10, which read 750 after the fish kill. The lake itself registered 500, with 200 being the acceptable limit, he said. He cautioned that one sample reading does not necesssarily determine the content of all the water.

There was a lake assessment done in 1996, which indicated that 97 percent of Ann's fecal count could be attribtuted to agricultural runoff, Hammer said. One percent was attributed to lawn runoff and septic systems that were not up to code, he said.

"The whole ditch system needs to be re-evaluted," Hammer said.

The situation was worsened by failing septic systems at Lake Ann, Hammer said.

Another fish kill was also reported at Lake Emma, which feeds into Lake Ann from the south.

The dead fish from Lake Ann were hauled to a pit at Harlan Yager's CRP land near Wright County Road 30 and disposed of, Hammer said.

Hammer could tell that something wasn't right when he noticed stressed fish coming close to shore July 3, he said.

In the past, a smaller fish kill was reported at Lake Ann of about 1,000 fish three or four years ago, Hammer said.

Other shallow lakes, such as Lake Ann, are expected to suffer during the hot summer months, Diedrich said.


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