On Aug. 11, 1913, shortly before 10 a.m., several people passing on the Main Street bridge in Pendleton noticed hundreds of dead fish floating down the Umatilla River. When they looked closer, they could see a large number of live fish as well, congregating at the dam just below the bridge. According to the story in the East Oregonian, “Every few minutes, one would expire and before dying would seem to be affected with a frenzy. With head above the surface, it would dash through the water at a great speed sometimes leaping clear out of the water on to the gravel bars. The sight attracted a large crowd and there was much speculation as to the cause of the mortality.”
Prominent members of the local fish and game association, including G.I. LaDow, C.K. Cranston and W.W. Hoch, were convinced there was some kind of poison in the water. Fingers pointed first at the Byers mill, suspecting it was being treated with cyanide, but employees there said that was not the case. It was pointed out that there were no dead fish between the mill and the penstock (where the water was diverted from the river by a gate to drive the mill’s wheel), and above the foot of the millrace there was no water in the river to speak of, so the poison had to have entered the water after it left the penstock of the mill and before it rejoined the river.
The strange situation apparently resolved itself within an hour, and the remaining fish recovered and swam away. It was mentioned in the article that a similar incident had occurred in the same place two years prior.
Most of the dead fish were suckers and pike, but a fair number of redside trout also were killed. Mr. Cranston inspected the insides of one of the fish but didn’t find anything out of the ordinary. The fish and game men did prevent people from picking up the fish for eating, however.
My first thought, as well, was some kind of poison. I read forward a couple of weeks and didn’t find a follow-up story, but forensic techniques were crude or non-existent in those days, so the chances of detecting poison in the water were pretty slim. My second thought was either a sudden increase in the temperature of the water (the article didn’t mention whether the day was particularly hot) or some other reason for a temporary decrease in the amount of oxygen available to the fish. That might explain the frenzied racing around exhibited by the fish. A third scenario might include some kind of predator trapped behind the dam harassing the fish, which might explain their leaping out of the water. I’m open to explanations from anyone out there more knowledgeable about the subject.