Hundreds of fish seen floating in Cibolo Creek at River Road Park Thursday may have left many residents surprised, but local officials said it’s a natural phenomenon caused by recent rains.
Boerne Communications Director Chris Shadrock said city staff quickly addressed the issue and reached out to the Texas Parks and Wildlife Department, which confirmed there was likely a dissolved oxygen crash caused by cool water being funneled into the creek from the recent rains after several weeks of hot and dry weather.
“The rain we received this week funneled cooler water into Cibolo Creek,” Shadrock said. “This caused what is known as a dissolved oxygen crash, which has impacted the fish population and is limited to the area in River Road Park by the dam. The Texas Parks and Wildlife Department confirmed this is likely what occurred.”
According to a factsheet published by the Ohio State University, Shadrock appears to have described a premature fall turnover where cooler, oxygen deficient water that rests at the bottom of a body of water is turned over or mixed with the nutrient and oxygen-dense warm layer at the top when cooler water dramatically impacts the surface water temperature. According to the document, this can lead to an overall reduction in oxygen across the entire body of water and cause a fish kill.
Shadrock said this was an unusual occurrence in Boerne. While it was a dramatic sight to see, with hundreds of fish floating at the surface along the section of the creek between the dam and the River Road bridge, Shadrock said some of the fish were able to be saved by aerating the creek, but a certain species of fish was more dramatically impacted than others.
“Since Wednesday morning, our Parks and Recreation Department has been operating water pumps along the creek’s edge to aerate the water and increase dissolved oxygen levels,” Shadrock said. “Thanks to their quick action, many of the fish that were struggling have recovered, but we know some fish did not survive. It is primarily the gizzard shad fish, which are the most vulnerable to adverse conditions experienced this week. If people visit the park things will look mostly normal. As we continue to monitor the conditions, visitors may see our crews out at the park, so please give them space to work safely.”
While some of the fish were able to recover, many were still lost, and a city employee could be seen Thursday morning netting out the deceased and putting them in trash bins.
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