Canal fish are cleaning up
The white amur fish that are used in Valley canals to help clear algae and weeds are finding so much to eat that they are growing larger.
One sure way to grow bigger fish is to feed them more, and that’s apparently what is happening in the canals that move water across Phoenix.
Every year, Salt River Project crews drain portions of the major canals so they can repair cracks, remove trash and clear debris. To do that, workers also have to move the white amur fish that live in the canals.
SRP uses about 50,000 of the fish, a species native to China, to help clear algae and weeds from the waterways that deliver about 1 million acre-feet of water a year to Valley residents.
First used by SRP in 1989, the amur fish primarily feed on weeds and algae that would otherwise slow the flow of water. Without them, SRP would have to use chemicals to manage vegetation levels in the canal.
And evidence suggests the fish have been gorging themselves lately.
SRP spokesman Jeff Lane said white amur fish recently pulled out of the canals measure between 40 and 45 inches. They’re typically around 30 inches during dry-ups, he said.
The large fish were found about 10 miles from Mesa’s Granite Reef Diversion Dam, which has heavy vegetation, he said.
While crews dry up the canals, they need to move the fish somewhere.
Because the canals are dried in stages, crews are able to move the fish to other parts of the canal system while workers perform maintenance.
Brian Moorhead, an SRP environmental scientist and engineer, watched the process from the Arizona Canal trail near 24th Street and Bethany Home Road in Phoenix. A giant crane outfitted with a net scooped the fish out.
“This area’s pretty clean,” he said. “Some places, you can have mud kneedeep.”
Rain can contribute to high levels of mud in the canal. Thankfully, he said, the first rain of the year did not set them back.
The sterile fish are brought in from Arkansas, because they’re non-native, and SRP officials make sure they have heads that are at least 2-and-1/4 inches wide so they can’t wiggle through the grates in the canal, Moorhead said.
Having wide-headed fish also means the canal grates can have fewer bars.
“The more bars you have, the less water can flow,” Moorhead said.
Cold conditions can also impede the fish’s work, he said.
“The fish stop eating at about 65 degrees, but vegetation can grow at 60,” Moorhead said. “We want them to eat all the vegetation.”
The SRP crews will move the fish to a portion of the canal near 48th Street and Indian School Road. The dry-up is scheduled to run through Feb. 5, according to an SRP release.
Moorhead said that crews moving the fish come close to moving every one. However, there are always a couple of small ones accidentally left behind, he said.
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