How could this be possible when the creek is more than 15 meters below the trail at that place?
The trout was fresh but dead already and part of the head was missing. It was a brown trout (Salmo trutta).
I do not think this trout was lost by a poacher because the trail passes along our home and the dogs would have alerted us. I bet on some fishing animal which may have lost its prey when the two dogs came running and barking.
This morning I found the solution: a grey heron (Ardea cinerea) which nest is located downstream, on the creek side, between the farm and the village. He just took off when we arrived.
In any case, our cats enjoyed so much the little piece of trout they got for dinner.