Sprinkle fish with 1/4 teaspoon salt and pepper. Dredge fish in flour.
Heat oil in a large nonstick skillet coated with cooking spray over medium-high heat. Add fish; cook 4 minutes on each side or until fish flakes easily when tested with a fork. Remove fish from pan; keep warm.
Add wine to pan, scraping pan to loosen browned bits. Add shallots, and cook until liquid nearly evaporates (shallots will be soft). Add chicken broth and lemon juice, and cook until liquid is reduced by about one-third. Remove from heat. Add butter, stirring until butter melts. Stir in remaining 1/4 teaspoon salt, parsley, and capers. Serve sauce over fish, and garnish with lemon slices, if desired.