Roughly chop celery root, onions, carrot, fennel, and leek and add to a large pot over medium-high heat. Add juniper berries, allspice, fennel seeds, and salt and stir to combine. Deglaze with white wine and add water.
Cut off fins of fish, slice behind gills, and make a long incision along the backbone. Turn over fish and repeat process on the other side. Remove fillets and set aside for other use. Bring stock to a boil, add fish carcass, simmer for approx. 5 min., and season with salt and pepper. Remove from heat and steep for approx. 20 – 30 min., or until flavor is at desired intensity. Enjoy!