Combine the fish bones, carrot, onion, celery, parsley, and salt in a large pot with a cover. Add enough water to submerge the ingredients and bring to a boil over high heat. Lower the heat to a simmer and cook, covered, for 30 minutes.
Strain the broth while hot and discard all the solids. Use the stock immediately, or transfer it to an airtight container and refrigerate it for up to o