Usually you put a decoy in the water that attracts fish and you spear it. You need a big hole to do this right. A Darkhouse is just that... dark. The darker the better. In fact, it takes a while to get your eyes used to the darkness after being outside. You would be amazed at how well this sometimes works, especially in clear water. Darkhouse spearing is usually used to target Northern Pike, although other species are sometimes targeted depending on that state's regulations.
When spear fishing you need to be able to block out the light so that you can see down into the water. To do this fishermen will use a darkhouse (a house without windows)
Its like wearing polarized sunglasses in the summer. With them on you can cut the sun and see down into the water. Without them all you can see is the glare on top of the water.
Fishing in a darkhouse can also be done when sight fishing. Which is basically just like it sounds. You'll actually look through the hole to see the fish below you, doing this allows you to pull the bait away from the small fish and hopefully more specifically target the larger fish.
Some guy in northern Minnesota was out spearing in his darkhouse with his Labrador retriever. The dog usually just sat and watched. Always keeping his eyes on the decoy and always getting excited when a fish swam into view this dog was truly a good fishing partner. Last winter as a large fish swam under the house the dog decided to take matters into his own hands. It jumped in the hole after the fish and actually swam after it. Both the dog and the fish disappeared from under the hole. His owner tried to get the dog back but there really wasn't anything he could do. The fisherman, obviously depressed, grabbed his gear and headed outside the darkhouse to pack it up. Just then the door on a nearby darkhouse flew open and a fisherman came running out screaming in fear. Right behind him was a very wet and cold dog. Turns out the dog found his way back to the surface through another guys hole and survived without any problems.
Imagine the other fisherman who was probably minding his business waiting for the right fish when a large dark object rises up from underneath the ice and comes splashing through the hole. panting, splashing and jumping out the water to catch it's breath the dog was just happy to find warm air. I think I would have had a heart attack.
This story is supposedly true. It was in a news paper up north and my girlfriends dad saved the news paper article.