Caldo de PescadoFish stock is quite easy to make and will improve the flavor of fine fish soups and stews. Chicken broth can be used instead and it's quite satisfactory (without distorting the desired fish flavor). I'm not wild about bottled clam juice and never use it in place of fish stock or chicken broth.An all-purpose fish stock is made with the bones and heads of mild-flavored white fish. Salmon, for example, makes a much stronger flavored stock that is fine if making a soup or other dish containing salmon; otherwise the general rule is to use the bones and heads of white fish. Buy fish stock bones from a reliable fishmonger. Remove the red gills from the heads, or ask the fishmonger to do it for you. The gills give an undesirable flavor to the stock.