A fish nicknamed "shellcracker" is being used to guard canals in Arizona against the quagga mussel, a destructive invader that has been found in lakes along the Colorado River.
Salt River Project, the largest water provider in the Phoenix area, has added 38,000 redear sunfish to its canals, hoping the fish's ability to crunch shells would help keep the mussel in check, said Brian Moorhead, an SRP environmental scientist.
"It is not expected to completely control the mussels," Moorhead said. "But we do think that it's better to put something in there to give us a chance and hopefully slow the mussels down."
The Central Arizona Project plans to stock the fish as well, said Bob Barrett, a CAP spokesman. Quagga mussels have been found at the Lake Havasu intakes to the CAP and in the first section of the aqueduct, which runs 336 miles to Phoenix and Tucson, Barrett said.
SRP is concerned because its system connects with the CAP at Granite Reef Dam in east Mesa, Moorhead said.
Using fish to naturally manage conditions in SRP's canals isn't a new idea, Moorhead said. SRP stocks two other fish: The western mosquito fish to help control mosquitoes and the white amur to control weeds.
Larry Riley, wildlife management coordinator for the Arizona Game and Fish Department, said introducing the fish is a step in the right direction.
"I don't know for certain how much good it will do in the long term," Riley said.
"But they certainly do eat mollusks and it may do some good."
The redear sunfish is native to the southeastern U.S. but isn't new to the state, Riley said. It looks like a bluegill, which is common in Arizona lakes, except for a red spot behind its eye. On a diet of snails, insect larvae and small crustaceans, it can grow to 11 inches and weigh up to four pounds.
Quagga mussels, native to Eastern Europe, were first found in Lake Mead in January. Since then they have been found in Lake Mohave and Lake Havasu.
The mussels breed rapidly and can cover underwater equipment and pipes, posing a threat to water delivery and canal operations, SRP's Moorhead said.
"All submerged equipment could be affected," Moorhead said. "With a mostly concrete-lined canal it's unlimited habitat for them. There is a chance large numbers of mussels could build up."
Combating the quagga mussel and its relative, the zebra mussel, has cost millions of dollars in the Great Lakes, along the Mississippi River and in other lakes and waterways in the Midwest and Northeast.
Quagga mussels were first seen in North America in the late 1980s.
There have been many attempts to get rid of the mussels in the Great Lakes, but none has succeeded in eradicating them, said Russell Cuhel, a senior scientist with the Great Lakes WATER Institute at the University of Wisconsin-Milwaukee.
Cuhel said it is impossible to say how effective the sunfish will be. He noted that many similar efforts have failed in the past.
"I'm not a fan of attempting biological control," Cuhel said. "The idea of introducing a predator in order to control another species in an ecosystem is the single-most failed management practice in the history of humans."