i use stock as stock. I don't think "Oh, this '86 Chateau Neuf will go delightfully as a splash in the pot whilst braising the organic free-range monkey brains, fed by virgin hands, and only lamb stock will do, that duck stock will clash terribly, what will the bridge club say?"

I say "hey, gonna make stock from this duck/crab and then strain it and pour it into an ice cube tray and then when I need a touch of liquid, gonna throw in a cube or two." I have yet to notice that crab stock changes the final flavor of a dish (altho I notice that it starts out smelling seafoody)

Stock is stock :)