This is the fastest, easiest and most humane way I have found to clean Dungeness crab prior to cooking. It was shown to me by a friend one day. Takes only a 5 gallon bucket which is what you probably already have the crab in anyway. And most of us have one or two around the house. Any edge would do I imagine or a cleat on the dock or boat as well.
I like to keep the crab cold once it comes out of the holding tank on the boat. I put ice in the bottom of an ice chest or 5 gallon bucket and lay a rag or plastic bag on top of it. Then I place the crab on top of that and cover them up so they relax and calm down. No water on them as they have a good bit inside their gill area already. And it is sea water which they came out of.
Step 1: Dungeness Crab Cleaning
After the crab cool down a bit they get slower and easier to handle. Pick one out of your cooler or bucket and hold upside down in the palm of your hand. Quickly slap the crab down on the edge of the bucket with the palm of your hand on top of it trying to aim for the center of the bottom of the shell. As you can see in the second picture I didn't quite hit center but no matter. The crab is immediately immobilized.
Step 2: Dungeness Crab
With both hands grab the claws and legs on each side and twist upwards and pull outwards. You now have the claw, legs and joints or knuckle in each hand and the carapace and guts fall away into your trash pile or bucket. On the knuckle you will have some beige gills hanging. With your finger just pull these off and discard into your bucket or trash pile. If the mandible parts are hanging on pull those off and discard. If there is anything other than white meat and shell shake it off and you should end up with a nice clean, ready to boil or steam crab legs, claw and knuckle.
I put these straight in a pot of boiling water. Use whatever flavoring you desire. I use 1/4 cup salt per gallon of water with enough water to cover the crab. 12 minutes of boiling. I start the time as soon as the water starts to boil again after adding the crab. Just a quick rinse under cool water to wash off any residue and so I can handle them.At this point they are ready to eat. Either to the table or quick chill down for storage. I always cook and eat so I can't tell you how long they will keep so use your own judgement as with all food preparation. I don't normally keep them for more than a couple days but I also enjoy them the most fresh boiled. Enjoy and share your secrets for the best recipe. We made our crab pots at Tech Shop. www.techshop.ws Welded them up from stainless. Made a couple from Rebar as well. Good luck!