OGALLALA, Neb. (AP) – Authorities say a lack of oxygen has killed dozens of rainbow trout in western Nebraska’s Lake Ogallala.  Nebraska Game and Parks Commission biologist Darrol Eichner told North Platte television station KNOP there’s a lack of oxygen in water near the lake bottom. Eichner believes the spillway that releases water from Lake McConaughey into Lake Ogallala is the problem. The mechanics of the release mechanism doesn’t allow much air to mix with the water as it is discharged from a gate at the bottom of the outlet chamber. Thus the fish aren’t getting as much oxygen in the water as they need. He says the fish kill has happened four or five times since the early 1980s and usually occurs in in late August and extends into September.