1Place fish and broth in 10-inch skillet. Heat to boiling. Reduce heat; simmer uncovered 5 to 10 minutes or until fish flakes easily with fork. Remove fish to platter. When fish is cool enough to handle, break into bite-size pieces, discarding skin and bones.
2In large bowl, mix fish, zucchini and radishes. In small bowl, mix mayonnaise, yogurt, ranch dressing and dill weed; fold into fish mixture. Cover; refrigerate at least 2 hours.
3To serve, toss fish mixture and spinach.