Cut each shrimp crosswise into thirds. Toss with ¼ teaspoon salt and set aside. Heat oil in a large saucepan over high heat until shimmering. Add reserved shrimp shells and cook, stirring frequently, until shells begin to turn spotty brown, 2 to 4 minutes. Add water, peppercorns, bay leaf, and 1/2 teaspoon salt and bring it to a boil. Reduce heat to low and simmer for 5 minutes. Strain the stock through a fine-mesh strainer set over a large bowl, pressing on solids with a rubber spatula to extract as much liquid as possible; discard solids.
Melt 1 tablespoon butter in now-empty saucepan over medium heat. Add onion, fennel, and remaining 1/4 teaspoon salt. Cook, stirring frequently, until vegetables are softened but not browned, 6 to 7 minutes (volume will be dramatically reduced, and onion will have mostly disintegrated). Add garlic and stir until fragrant, about 30 seconds. Add rice and cook, stirring frequently, until grains are translucent around edges, about 3 minutes.
Add wine and cook, stirring constantly, until fully absorbed, 2 to 3 minutes. Stir 2 cups of stock into the rice mixture; reduce heat to medium-low, cover, and simmer until almost all liquid has been absorbed and rice is just al dente, 16 to 18 minutes, stirring twice during simmering.
Add 1/2 cup stock to the risotto and stir gently and constantly until risotto becomes creamy, about 3 minutes. Stir in the Parmesan and shrimp. Cover saucepan and let stand off heat for 5 minutes.
Gently stir in the chives, lemon zest, juice, and 1 tablespoon butter into the risotto. Season with salt and pepper to taste. If desired, stir in additional stock to loosen the texture of the risotto. Serve, passing lemon wedges and extra Parmesan separately. Enjoy!