Ever find rocks (pebbles) in a lings stomach?

I found two 1/2-3/4" rounded red rocks in a ling today.   I'm not too surprised, considering the lures they'll hit, I've just never seen it before.  Maybe they ate a critter that ate the rocks?  They'll often barf up their stomach contents when in a fight for their lives.

I've found some crazy things in their stomachs but never rocks...interesting though. It doesn't surprise me!