The agency also thanked an unnamed local child, who had noticed the dead fish and alerted them to it.

It said in its Facebook post: “We are very grateful to a 12-year-old boy who removed fish from a small stretch of the river, put them in his bucket, then staged a photograph for us.”

The agency was spraying hydrogen peroxide and aerating the water in an effort to clean up the river and rejuvenate its oxygen supply.