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Fish kill at Dunes club’s lake due to depleted oxygen level

By Staff | Jan 15, 2009

A large number of fish were discovered dead on Sunday in a lake at The Dunes Golf and Tennis Club, prompting a number of calls to club management as well as the City of Sanibel’s Department of Natural Resources.

Golf club staff members have been dealing with the situation to the best of their ability, manager Craig Colton reported.

“We’ve got crews out there a couple of times a day, netting the fish and cleaning up,” he said, pointing out that two pumps were operating non-stop in a somewhat futile effort to inject air into the affected lake for the surviving fish.

“We can’t make it rain,” Colton added, just as a passing cold front drizzled some much-needed precipitation across the island on Tuesday afternoon.

This is the second fish kill that Colton has seen at The Dunes Golf and Tennis Club since starting as manager more than a year ago. Both times, the island was going through somewhat of a dry spell, he said.

“Rain introduces not only water but oxygen to the lakes,” he explained. “Without it, we get a problem.”

Rob Loflin, Director of the City of Sanibel’s Department of Natural Resources, attributed the kill to dissolved oxygen, whereby there was not enough oxygen in the water for fish to breathe.

“The surviving fish can all be seen at the surface right now, trying to get air,” said Loflin.

Affected species include snook, blue crab, tarpon and tilapia, among others.

Although fish kills are a common phenomenon, occurring almost every year in some body of water on Sanibel, it is rare to have such large species affected, said Loflin. Fish kills resulting from depleted oxygen resources usually occur after severe temperature changes or other weather fluctuations. However, added Loflin, it can also occur during a phenomenon known as inversion, when the lower layers of a body of water become completely depleted of oxygen.

“A turnover event takes place,” he said, “where the anoxic waters move to the top, depleting the entire body of water of oxygen.”

Loflin stressed that it as not yet clear what caused the depleted oxygen levels in the lake, and that nutrient runoff from fertilizers could also be one of the culprits. In an effort to prevent fish kills that could be related to nutrients from runoff, Loflin said he will be working with The Dunes Golf and Tennis Club to develop a vegetation plan that will help to absorb those nutrients before they have a chance to run into the lakes.

In addition, Colton said that he and his staff have been working closely with the city’s Natural Resources staff, and he looks forward to their long-term recommendations to prevent future fish kills whenever possible.