Exotic fish are being dumped into Tucson area park ponds, threatening the survivability of native species, a Pima County parks official said Thursday.

Kerry Baldwin, the county’s Natural Resources, Parks and Recreation Department division manager, said urban water sources such as Agua Caliente Park on Tucson's east side quickly get “contaminated by exotic animals and fish”.

“We could not maintain the native species because of the exotics (in the long term),” Baldwin said. “The exotics are more dominant and over time, they will take over.”

Baldwin said the county wants to introduce native amphibians and reptiles back into the ecosystem at Agua Caliente, but native species don’t do well in the presence of the exotics. Many of the wildlife that visitors see there, such as red slider turtles, are from elsewhere.

Baldwin and environmental education program manager Wendy Burroughs both said it is difficult to identify all the species that live in the main pond at Agua Caliente Park.

“People get tired of their goldfish, but they don’t want to get rid of it to another person and they don’t know what to do with it,” Baldwin said. “So what do they do? Oh, there is a pond out at Agua Caliente. Let’s go put 'Fred' in the pond.”

The law prohibits releasing or abandoning pets or wildlife, and warning signs are posted at parks. However, Baldwin said the signs are often ignored.

Yoohyun Jung is a University of Arizona journalism student and intern at Arizona Public Media.