Court-bouillon is a traditional poaching broth for fish. Store the broth in airtight containers, and refrigerate for up to 3 days or freeze for up to 3 months.
Fill a large stockpot with the water (it should be about 3/4 full). Bundle thyme, parsley, peppercorns, and fennel seeds in a small piece of cheesecloth to make a bouquet garni, and place in stockpot. Add remaining ingredients.
Cover pot, and bring to a simmer over medium-low heat. Remove lid; gently simmer 30 minutes. Remove from heat; discard bouquet garni. Use immediately, or let cool completely before storing.