Fish were discovered dead in the creek Friday night.
Lower Susquehanna Riverkeeper Michael Helfrich said patrons at the Waterway Bar and Grill called him around 7:40 p.m. and said they saw hundreds of dead fish in the Codorus Creek.
Helfrich went to the College Avenue bridge near his home and saw dead fish there as well. He headed to the Waterway to talk to the patrons and check on the fish there, then began working his way upstream to try to find the source of the problem.
Emergency responders from the environmental protection department arrived after 8 p.m., and Helfrich worked with them to track the dead fish upstream. They traced dead fish to above the Richland Avenue dam, he said, but then saw no dead fish at the Indian Rock Dam bridge or points further upstream.
Lisa Kasianowitz, spokeswoman for the department of environmental protection, said responders were on the scene until around 2 a.m. She said the state responder estimated seeing about 50 to 100 dead fish. Helfrich said the patrons at the Water Way had reported seeing about 300 dead fish, and he estimated the total was higher than that.
According to DEP and Helfrich, the dead fish were shad and sucker. Kasianowitz said there were other fish in the creek that were fine. "That's an indication it's only a single event and not a recurring event," she said.
The state responders took water samples, which will be sent to labs for testing. Two tests -- a pH test and a dissolved oxygen test -- were performed on site and turned out normal, Kasianowitz said.
It will take about a week for the water sample to be tested, she said.
"DEP takes fish kill seriously," she said. "Anything that enters Pennsylvania waterways, we definitely investigate and follow up. We will want to try to find the source."
Also of interest When the Codorus Creek made like a river
About the Northwest Triangle and skinnydipping in the Codorus