A fish harvester for the automatic and humane slaughter of fish comprises a fish accommodating space having an entrance for insertion of a fish and an exit for removal of a fish. The harvester includes means for positioning and retaining a fish, a slaughtering member for slaughtering a fish by contact with some portion of a fish; and driving means for driving said slaughtering member. The slaughter member preferably includes spikes for insertion into the brain of the fish. The harvester preferably automatically severs a major blood vessel in order to allow bleeding of said fish. The harvester preferably automatically gauges the size of the fish and positions the fish and the slaughtering member relative to each other, with reference to the size of the fish, in order to allow effective operation. A method of automatically slaughtering fish is also provided.