Hundreds of fish were seen floating on top of the water at Buffalo Wallow Park in Odessa on Wednesday.
The city of Odessa Parks and Recreation department says the the fish died from depleted oxygen levels in the water.
Steve Patton says this happens a few times a year when run off from surrounding parking lots pollutes the water. The run off causes algae to grow, which in turn depletes oxygen flow.
The city tries to aerate the water as much as possible, but they often can't keep up with the amount of pollution.
Rain is needed to help freshen the water and keep the lake from being stagnant.
Patton says the fish were removed and the carcasses were planted at a tree farm to use as fertilizer.