Smallmouth bass posing a threat to native fish in Arizona's Fossil Creek

PHOENIX – Nonnative smallmouth bass have been detected above both the permanent and temporary man-made fish barriers along Fossil Creek, which is a unique fishery and haven for native fish including roundtail and headwater chub, said Arizona Game and Fish Department officials.

“Right now we can’t say for certain how the smallmouth bass got above the upstream temporary barrier at Fossil Creek,” said Fisheries Chief Kirk Young. "These bass definitely pose a threat to the native fish in this rare stream."

The bass could have migrated upstream before the temporary barrier was constructed, possibly gotten past the temporary barrier, or somebody could have illegally introduced them. 

Six of the nine smallmouth bass observed recently have been removed, and biologists are back at the creek this week going after the remaining known nonnative fish.

“There are lots of places for fish to hide in this rare travertine stream, so while we will work hard to physically remove the smallmouth, there aren’t any guarantees,” Young said.

Game and Fish biologists are working with U.S. Fish and Wildlife Service, Forest Service, and Bureau of Reclamation to address the long-term goal of removing any smallmouth bass and ensuring the fish barrier works as intended.

Shaula Hedwall, a fishery biologist with the U.S. Fish and Wildlife Service, said the best strategy is to take one step at a time and have everyone working together on common objectives. “In fact, at Fossil Creek, a multitude of agencies and partners have a remarkable history of working together to overcome obstacles.”

The fish barrier on the lower end of Fossil Creek was constructed in 2004, and at that time, a large multi-agency effort involving many stakeholders successfully removed all nonnative fish from this unique travertine stream. Prior to the renovation, nonnative fish were one of the primary causes for the decline of native fish in Fossil Creek, and their presence now threatens all of the native aquatic species in the creek, including the unique native sport fishery.

It also took a major effort to restore the historical flows to Fossil Creek – a significant portion of those flows had been diverted for hydro-electric generating purposes for almost a hundred years to help Arizona grow and flourish.

Not long after the fish barrier was constructed, the nonnative fishes removed, and the flows restored, the Game and Fish Commission established a unique seasonal catch-and-release-only roundtail fishery along a section of Fossil Creek.

For years, the fish barrier worked as designed. However, a flood event in the winter of 2010 impacted the barrier. An attempt was made to fix the barrier, however in July of 2011, nonnative smallmouth bass were detected above the barrier.

A temporary fish barrier was constructed about two miles upstream of the original barrier in August of 2011. This temporary barrier was placed at a site believed to be upstream of the known distribution of the smallmouth bass that had gotten above the downstream barrier.

“Obviously our primary goal at this time is to remove nonnative fish from above the fish barriers at Fossil Creek. The one guarantee we have is there are lots of folks willing to work diligently together to make that happen,” Young said.

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