The state of being a fish, or of belonging to the world of fish; fish collectively.
1922, Thomas Morris Longstreth, The Laurentians: The Hills of the Habitant, page 286:In the ouananiche, fishdom has achieved its glittering perfection.
2005, Robin Cody, Ricochet River, page 83:Some kind of homing instinct—imprinting, they call it—guides a salmon to the very same mountain stream where it hatched and awoke to fishdom.
2008, H. W. Rardin, It's Always Windy on Trash Night: And Other Facts of Life, page 232:Meanwhile on shore you get all pumped because your line is jiggling and you are completely unaware of the social protocol of fishdom occurring below the water line.