CIOPPINO (CLASSIC ITALIAN SEAFOOD STEW)

2 tablespoons olive oil 1 fennel bulb, thinly sliced 1 onion, chopped 1 large shallot, chopped 4 garlic cloves 1 tablespoon tomato paste 1 (14 oz. can diced tomatoes in juice) 1 bay leaf 1 pound uncooked large shrimp, peeled/deveined 3/4 pound assorted firm fleshed fish fillets such as...