Lol I don't think any North American crayfish get to twelve inches. Also, this picture looks more like an alleni than a clarkii, but the stripe on the tail isn't an alleni trait, as far as I know. But if it is an alleni, the total lack of pigment would get rid of the most defining alleni feature which is darkened spots above the gill openings on the face. A picture of Mr. Crabby would be helpful, just to make sure.