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Goldfish found in Renner Reservoir

April 15, 2020
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Cody - Recently, invasive goldfish have been discovered in Renner Reservoir near Hyattville.  The goldfish, likely the result of illegal stocking, will have far-reaching consequences to the newly rehabilitated reservoir and bass fishery.   

Fisheries Biologist Joe Skorupski said the illegal stocking of goldfish will change the ecological dynamics of the fishery and complicate management strategies focused on largemouth bass.  “This is very disappointing and frustrating as a fisheries manager,” Skorupski said.  “Especially after Game and Fish recently invested over $324,000 to rehabilitate the reservoir infrastructure and largemouth bass fishery.”

Under the right conditions, goldfish will proliferate, binding up resources that could be used by largemouth bass.  Goldfish are fast growing, with mature individuals averaging about 12 inches, but can grow to 19 -23 inches; all sizes that cannot be preyed on by largemouth bass.  “This is not ideal for the fishery or fishermen seeking an outstanding angling experience Renner was once known to be,” Skorupski said.  

During a survey on April 1, Skorupski documented over 500 goldfish of multiple age classes ranging in size from 3 to 6.5 inches.  This indicates that natural recruitment is occurring in the reservoir and will continue.  Based on this data, goldfish were likely illegally stocked in 2018.  Individual fish will be aged to better understand the population structure of this illegal introduction.

“Fisheries management crews in Cody are committed to Renner Reservoir's success as a fishery,” Skorupski said.  “However, the illegal stocking of goldfish greatly complicates this scenario and puts a successful outcome at risk.  Further it will require additional time and effort to work on this threat that could have been spent on other high priority fisheries issues in the Bighorn Basin.”

During a survey on April 1, Game and Fish documented over 500 invasive goldfish ranging in size from 3-6.5 inches in Renner Reservoir.

- WGFD -

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