Dead fish are floating to the surface in the UC Davis Arboretum, reportedly after two nights of aerial pesticide spraying -- but apparently that's not what caused the fish to die.

Assistant Arboretum Director Andrew Fulks says the aerial spraying and the fish kill are a coincidence and not a cause. 

"While the timing was terrible on this, people will draw the line between the two dots. But fortunately they were not connected," Fulks said. 

So what did kill the mosquito fish, carp and other species? 

"What we suspected and based on what we've learned since yesterday, the fish kill was a result of a depletion of oxygen in the water," 

Fulks says the heat and drought lowered the water level and warmed the water, which bloomed with algae, which uses a lot of oxygen. That is what led to the fish dying. 

Fulks hopes this will put neighbors and visitors to the arboretum at ease about the spraying to cut down on mosquitoes in the area that may carry West Nile virus.