Whisk together flour, baking powder and salt in a small bowl. Set aside. In a medium bowl stir egg, sardines with juice, zest and juice of lime and onions. Stir flour mixture into sardine mixture. Heat approximately 2 inches of oil in a large nonstick pan. Measure about 1 tablespoon of fritter into the oil and cook about 1 minute on each side or until the fritter is a golden colour all over. Remove with tongs and let drain on paper towel. Serve over a bed of bean shoots and decorate with quartered limes.