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Renner Reservoir rehab nearing completion

April 29, 2019
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Minnows recently stocked

Cody - A project focused on bringing back the bass fishery in Renner Reservoir is near completion.   Recently 2,000 fathead minnows were stocked in the 70 acre reservoir south of Hyattville.  The minnows will serve as forage fish for bass that will be stocked within a few months, after the reservoir completely refills with water. 
Historically, the reservoir produced quality largemouth bass fishing and was popular with local and traveling anglers alike.  In 2014, the bass fishery was lost following a near complete winter-kill and over the last three years, Game and Fish has pulled out all the tools in the toolbox to bring this fishery back.
While the loss of the bass fishery in 2014 was unfortunate, ultimately it presented Game and Fish with an opportunity to address key limitations fisheries biologists had been struggling to manage over the last decade.  For years, the reservoir was plagued by winterkill events and dense vegetation, which unraveled the fishery and stunted the bass and sunfish population. 
The rehabilitation process began in summer of 2016 when the dam was breached to drain the reservoir.  Fisheries Biologist Joe Skorupski said draining the reservoir accomplished several things.  “First, it removed the stunted sunfish population that thrived in the reservoir due to shallow habitat and dense vegetation,” Skorupski said. “Secondly, it allowed access to replace the outflow structure and add a water feature at the inflow pipe and accomplish dirt work to improve fish habitat.”
The project has not been without challenges.  “Due to unforeseen logistical issues and challenges, the project has taken longer than expected,” Skorupski said.  “When Game and Fish embarked on this project in 2016, it was estimated to take approximately two years.  We appreciate angler’s patience throughout the project and acknowledge that the time lost at Renner has been difficult.” 
One of many challenges encountered during the project was the presence of natural springs under the reservoir.  Once drained, several natural springs were discovered, causing dry time to take substantially longer than expected.  Some areas never dried out completely and ultimately affected the extent to which Game and Fish could modify and improve fish habitat.
Despite challenges, Game and Fish Habitat and Access crews were able to dig out a deep pool near the casting platform and create a channel from the boat ramp to the inlet structure to increase depth.  They were also able to create a water fountain with the inlet structure, which will improve oxygen levels and reduce the chance of winterkill.  Once dirt work at Renner was completed, crews focused on fixing the outlet structure which had not been functional for more than a decade.  The new outlet structure provides flexibility to change water levels, which allows for better management of wintering conditions for fish and management of vegetation.   
Last fall, repairs to the dam were completed, a new concrete boat ramp was poured and the reservoir began filling. 
In an effort to jump start the fishery, Game and Fish planned to transplant catchable sized bass from another water body, in addition to stocking smaller bass.  “Due to concerns with disease, fisheries managers have decided to forgo transplanting larger bass,” Skorupski said.   “Fingerling bass from a hatchery will be stocked within a few months.”
Despite challenges and setbacks, the end result of the project will be a healthy and more stable bass population in Renner Reservoir for anglers to enjoy.

In July 2016, the dam was breached to drain the reservoir.  

Due to the presence of natural springs, the reservoir floor did not dry out as much as expected once drained, causing logistical issues with heavy equipment.    While crews were able to dig out a small section and channel to increase water depth for fish, ultimately the mud affected the extent to which crews could modify and improve fish habitat.   

The design of the new inlet structure will improve oxygen levels and reduce the chance of winterkill. 

The new Agri Drain outlet structure will allow managers to better control water levels in the reservoir. 

Fisheries biologist Joe Skorupski releases fathead minnows in Renner Reservoir.  The minnows will serve as a forage base for bass that will be stocked in July.  

An adult fathead minnow that was recently stocked in Renner Reservoir.    

- WGFD -

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