Heat olive oil in a large sauté pan. Add garlic and fennel, and cook on medium heat, stirring often, until the fennel pieces begin to soften, about 5–7 minutes.
Add tomatoes, chicken broth, and potatoes, and bring to a boil. Lower temperature to a gentle simmer, and cook until the potatoes begin to soften, about 10 minutes.
Add shrimp, oregano, lemon juice, and basil, and mix gently. Continue to simmer until the shrimp are pink and fully cooked, about 5 minutes (to a minimum internal temperature of 145 °F).
Add salt and pepper.
Serve 1½ cups stew (each serving to include about six shrimp).