Found this recipe since dogfish urinate through the skin. I guess removing the skin and bleeding it out asap is a must.
Maybe this tough skin is not so easy to pull off quickly and the reason no one wants it. Oh and the fact they are so ugly.
Article-
"I have always fished for shark. Of course, in the deep southern atlantic states, the fish are a little bigger than the dogfish here. But, that's ok.
When I catch a dogfish, I am happier than a pig in slop.
What I do is slit the throat as soon as I pull the hook out. Then, I peel it like a catfish: cut just deep enough to break the skin in around the base of the tail and fins then, using pliers, grab the skin and pull the skin off the body and over the head.. After that, open in the belly cavity and yank the gunk out. Throw the gunk and skin in a ziplock bag.
At home, cut the fish from end to end along the spine, then spice with some good, not cheap, cajun spices that have been cooked with some butter and lemon juice. Place on a sheet of foil, wrap all the way around and broil for 20 minutes.
Super good !!!
People around here that have have tried dogfish before and refused to eat it again and eaten mine always want more.
So, if anyone around Nanaimo catches them and don't want them, please let me know, I'll take them with a big smile and thank you !!!"
wow-
http://www.break.com/index/dogfish-refuse-to-be-cooked-and-eaten.html