Unique Characters: Upper margin of lower jaw rises sharply. Back blue-green. Usually a pale peritoneum. Larger eye, diameter greater than snout length. Usually 39-41 gill rakers on first gill arch.
Blueback Herring Alosa aestivalis. Bluish back. Usually one dark spot behind upper edge of the opercle. Black peritoneum. Diameter of the eye is equal to or less than the length of the snout. Usually 44-50 gill rakers on lower limb of first gill arch.