Heat the olive oil in a small skillet. Add the sliced garlic and cook over low heat until golden, about 1 minute. Add the chopped lemon and cook over moderate heat until slightly softened, about 2 minutes. Scrape the lemon relish into a small glass or stainless steel bowl and season with salt and pepper.
Wrap 3 slices of bacon around each trout or herring fillet. Secure the bacon with toothpicks.
Heat a large skillet over moderately high heat. Add the bacon-wrapped trout fillets and cook until the bacon is browned and crisped and the fish is just cooked through, 3 to 4 minutes per side. Transfer to plates, spoon the lemon relish on top and serve.
Make Ahead: The lemon relish can be refrigerated overnight. Reheat gently before serving.
Wine Recommendation: A light, lemony Riesling won't overwhelm the delicate flavors of the trout and will provide a crisp yet fruity contrast to the smoky bacon. Look for a German Riesling Kabinett from the Mosel, such as the 1999 Ockfener Bockstein Dr. Fischer, or a bright Riesling from New Zealand, such as the 2000 Villa Maria Private Bin Marlborough.