Hikers in southern Germany discovered 80 live fish in the grass next to a mountain trail in Bavaria on Sunday, according to police.
The hikers immediately reported the carp to the authorities after spotting the live fish on the side of the trail near the town of Harburg, police said, but none of the fish survived.
Investigators believe that unknown perpetrators likely threw the live fish into the grass from a vehicle. The trail runs near an electric transmission line.
Police have launched a criminal investigation into violations of Germany's Animal Welfare Act.
According to the local veterinary office, the fish were previously healthy and no signs of disease were found.
A motive remains a mystery to the police.
"Why would I drive up a mountain and throw some massive, large carp next to a transmission mast?" a police spokesman said on Tuesday. "That makes no sense at all."