Halibut Chowder Stock For Free

At our local grocery store when they have a special on fresh Halibut, and it says "whole" once the fish is cut up, the backbone, and tail pieces are discarded to be thrown away. This makes the best soup stock and is meaty enough to make a wonderful chowder. Ask if you could have some. They did it the last two times I have seen the fish on sale. I got two pots of halibut chowder stock and it was free! This also works for salmon.