Wyoming Game and Fish plan to spray algaecide at Renner Reservoir in spring 2021 - Casper, WY Oil City News
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Wyoming Game and Fish plan to spray algaecide at Renner Reservoir in spring 2021

(Wyoming Game and Fish Department)

CASPER, Wyo. — The Wyoming Game and Fish Department have been looking for ways to address an overabundance of an aquatic algae called chara at Renner Reservoir.

“Whether you visited Renner Reservoir for the first or tenth time this summer, you probably noticed a branchy, aquatic algae called chara covering the bottom of the reservoir,” Game and Fish said in December.

The department treated two small portions of the reservoir with an algaecide in August in an effort to learn how to effectively control the excess growth of the chara. Different doses of algaecide were sprayed at the two areas.

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Game and Fish found that the almost all of the chara was killed within a week. The department reassessed the area in early November and found little regrowth “suggesting longer-term effectiveness of the treatment.”

The department plans to conduct spraying across the reservoir in the spring.

“Compared to other aquatic plants, which are referred to as macrophytes, chara forms denser mats offering less habitat for fish and a less palatable meal for invertebrates,” Fisheries Biologist Joe Skorupski said. “At high enough densities, chara can have negative ecological impacts on aquatic environments and be a nuisance to boaters and anglers. It’s fair to say that the density of chara in Renner is high.”

Aquatic vegetation serves as an important food source and habitat for macroinvertebrates and can also help stabilize sediment and offer cover for fish. However, Game and Fish said that chara provides less benefit than another aquatic vegetation species at Renner Reservoir called coontail.

“By treating chara, we hope to give the higher quality vegetation a chance to flourish which would benefit the small reservoir,” Skorupski said. “Spraying early in the growing season will give other high quality plants a chance to better establish and is more cost effective.”

“The spring application approach will be safe for the fish population. Monitoring of spraying success and regrowth of chara and other macrophytes will be completed throughout 2021.”

“A test plot in Renner Reservoir 69 days after treatment showing nearly 100% effectiveness in removing chara.”  (Wyoming Game and Fish Department)