Fish in Tempe Town Lake may be dying, but the water is safe for humans

The dead fish and golden algae may smell and look bad, but experts say swimmers and boaters need not fear

A large number of dead fish have floated to the top of Tempe Town Lake recently due to fluctuating temperatures and algae counts, but experts say they are likely not harmful to people who use the lake for recreation and sport.

Joann Hill, community fishing program specialist for the Arizona Game and Fish Department, said the fish are not harmful unless eaten. 

Hill said most of the dead fish are tilapia, a species native to the warm waters of Africa, and that when water temperatures drop below 55 degrees, they die. Hill said the other species that has been dying, shad, also can't survive in cooler waters.

She said golden algae is also present in the lake and contributes to the water's odor and murky color. She said the algae isn't killing the fish, but it doesn't help the condition of the lake. 

But golden algae is not dangerous to humans – it only affects gilled organisms. 

"You could even drink (the water)," she said. "It just doesn't look pretty, and it smells bad."

Hill said a consultant is monitoring the lake daily to help the department resolve the problem.

Julia Jankuski, a biological sciences junior, is the president of the ASU Triathlon Club

Jankuski said the team does not often use the lake, but almost every time they do someone gets sick.

She said there are many events held in the lake, including triathlons such as the Ironman competitions and this year's NCAA triathlon championship.

"I personally haven't witnessed the dead fish in the lake, but when we run around it it smells awful," she said. 

Jankuski said many of her team's athletes choose not to participate in races at Tempe Town Lake, especially ones who are susceptible to illness.

To do open-water swims, the team generally travels to Saguaro Lake because Tempe Town Lake is not always open for swimming. But she said even if it was available, the team would be hesitant to use it. 

Spencer Kolesar, a freshman studying construction management, said he often runs by the lake to train to join the military, and that it has smelled worse than usual the last few weeks. 

"It wasn't horrible smelling the whole time," he said. "But every other half mile I'd catch a whiff of something bad. The 202 is right there, so that could have been a factor, but there were times it smelled by the lake."

Kolesar said he recently spotted a dead fish every hundred yards or so while training near the lake. He said when the algae and dead fish became apparent, the smell got worse.

"I would not be inclined to swim in Tempe Town Lake," he said.

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