Wildlife officials say we'll probably never know how many game fish and bait fish died in a large fish kill last week at Youghiogheny Dam in Confluence. Officials of the U.S. Army Corps of Engineers and Pennsylvania Game Commission were alerted to the fish kill by a local resident who reported he saw "thousands" of fish, including walleyes up to 30 inches, floating belly up below the dam.

The incident occurred while the already low, cold reservoir was rising. Discharge gates were opened to prevent rising waters from interfering with the work of a PennDOT crew that was removing a boating hazard from a former bridge pier. Fish from throughout the 3,566-acre reservoir had clustered in deep water near the dam -- the warmest point in the lake -- and were drawn into the flow when 60-feet-deep discharge tubes were opened.

Greg Brant, project operator for the D/R Hydro Company, which makes electricity at the dam, said 4,450 cubic feet of water per second was released during the unusual late-season discharge. The normal discharge this time of year is under 1,000 cubic feet per second.

The fish were killed when their air sacs burst from a change of air pressure as they plummeted down through the dam's bypass gate and, to a lesser extent, through the hydro works.

Rick Lorson, a biologist with the Pennsylvania Fish and Boat Commission, said fish killed in this way may wash up miles below the dam. An accurate count, or even a reasonable estimate, of the kill would be problematic, he said, but the impact on the lake's fishery should be minimal, particularly among larger fish.

"The colder water put stress on the alewives, particularly," he said. "They get lethargic in the cold and get pulled through the discharge tubes and the walleyes follow. But there's enough [alewives] that the population won't be hurt by this, and compensatory survival will occur with the walleyes -- those of smaller size will take the place of the few larger fish that were killed."