Court documents say Donald Earl Fite III wanted to reunite with the woman in July, but she wasn't willing. Fite shoved her against a wall and tossed her against a bathtub. The woman fled, then returned to find her fish on the floor with a knife through it.
Court documents say Fite told an officer, "If she can't have me, then she can't have the fish."
The Oregonian newspaper reports Fite declined comment Tuesday. His attorney, Tom Macnair, said stabbing the fish was "a very low point" in his client's life.
Fite pleaded guilty to animal abuse and domestic-violence assault.