Fill a large heavy-bottomed pot with cold water. Add the fish bones, peeled onion, peeled carrot, celery, parsley and the whole black peppercorns. Bring the water to a boil over medium-low heat and simmer for 25 to 30 minutes.

Lightly salt the broth and use a slotted spoon to skim off the foam that will form on the surface of the broth until clear. Once the broth is done, pour it through a chinois.
Now you can use the fish broth for other recipes.

Fish broth can be stored in the fridge for 2 days or in the freezer for a couple of months.