Science

Thousands of fish are hard at work keeping Arizona canals clean

KJZZ | By Alex Hager

Published February 23, 2026 at 8:02 AM MST

Carp splash into a Salt River Project canal in Tempe, Arizona on February 13, 2026. The agency uses thousands of fish to keep the canal from getting clogged with aquatic plants. — Carp splash into a Salt River Project canal on Feb. 13, 2026. The agency uses thousands of fish to keep the canal from getting clogged with aquatic plants.

In the cool dawn of a February morning, a crew is assembling to do maintenance work on a water canal in Tempe. This crew will spend the rest of its life in the canal, removing the plants that stop water from flowing. That’s because the workers aren’t human — they’re fish.

The Salt River Project, which operates this canal, estimates that about 44,000 of these fish live in its canal system. This morning, it’s adding about 1,000 more.

The fish are a species of carp called white amur. They’re native to Asia and especially adept at eating the aquatic vegetation that grows along the walls of the canal. Those plants can slow down the water and make it harder to send to faraway users of the canal or gum up the intakes that divert water in different directions.

A white amur flops in a net in Tempe, Arizona on February 13, 2026. The species is not native to the U.S., so SRP only uses fish that are unable to reproduce. — A white amur flops in a net in Tempe, Arizona, on Feb. 13, 2026. The species is not native to the U.S., so SRP only uses fish that are unable to reproduce.

Brian Moorhead, an environmental scientist with SRP, said it’s cheaper and easier to use fish than humans when it comes to removing those plants.

“It's been a long day of pulling a lot of very heavy vegetation out of the canal,” he said. “Very labor intensive and expensive. The fish come in 24/7. They're happy to eat. It just makes their day.”

This latest batch of fish arrived by tractor trailer. With the truck idling on a bridge over the canal, a worker walked on a narrow platform along a long tank towed behind the cab. He unscrewed a stopper on the side of the tank, attached a metal tube, and let the fish slide into the canal like kids at a waterpark.

Brian Moorhead, an environmental scientist with the Salt River Project, stands near a canal in Tempe, Arizona on February 13, 2026. He said fish are cheaper and more effective at cleaning plants out of the canal than human workers. — Brian Moorhead, an environmental scientist with the Salt River Project, stands near a canal in Tempe, Arizona, on Feb.13, 2026. He said fish are cheaper and more effective at cleaning plants out of the canal than human workers.

He repeated the process a few times until about a thousand had made it into the water.

They’ll have their work cut out for them, since vegetation in the canal can grow up to a foot a day, according to Moorhead. SRP has been using the fish going back to the early 1990s, and this year’s batch cost the agency about $250,000.

“These guys are doing canal maintenance all day long,” Moorhead said. “They don't mind weekends or holidays.”

While the fish are non-native, there are measures in place to keep them from spreading throughout the state. The kind used in the canals are unable to reproduce, and they are penned into the canal by grates with openings too small for them to pass through.

Moorhead said anglers are supposed to release any white amurs they catch.