Stormwater Runoff Killed More Than 12,000 Fish At Espada Park

click to enlarge Stormwater Runoff Killed More Than 12,000 Fish At Espada Park
San Antonio River Authority
Rain can be a blessing and a curse in San Antonio. For 12,525 fish near the San Antonio River in what's called the Espada Ditch on the South Side, this week was a curse.

San Antonio River Authority biologist Shaun Donovan said a cocktail of stormwater runoff that likely carried pesticides, herbicides and gasoline combined with low oxygen in warm water caused a mass die-off of 12 to 15 species of fish. Donovan says it's not uncommon to have fish kills during the scorching Texas summer, but kills of this size are unusual. "The irony is the rain started it and the rain kind of helped it out," Donovan said. Rain on Wednesday helped re-oxygenate the water and dilute any toxic substances in the water after it flushed toxic runoff from fields and roads into the Espada Ditch on Monday.

On Tuesday, workers doing regular maintenance in the area noticed a few dead fish. They also saw other fish struggling to the surface for air so they reported it to SARA. When Donovan and a team of SARA biologists showed up Wednesday morning to check on the situation, there were thousands of dead fish. "We saved 700 to 900 fish on Wednesday from 7:30 to noon," he said. "After that, it became a dead fish removal process."

Two-thirds of the dead fish were gizzard shad. The majority of the rest of the fish were bluegill sunfish and longear sunfish. "Those are all native species," Donovan said. "We hate to lose them." Because of the sheer size of the mass kill, Donovan said it will take time for those populations to rebound. "We're sure that there are still fish in there, but their populations are significantly diminished," Donovan said. "So it will just take some time."


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