The carp die-off has forced cancellation of the Carp-O-Rama at Lake Maloney State Recreation Area south of North Platte.
The Nebraska Game and Parks Commission Family Fishing Event had been scheduled for Saturday.
The fish carcasses are being analyzed to determine the cause of death.
Another Family Fishing Event for the North Platte area is scheduled Aug. 8 at Iron Horse Lake, from 6 p.m. to 8 p.m.
Loaner fishing equipment, bait and advice are free, but all participants age 16 or older must have a valid fishing permit.