Gill rakers shorter and more widely spaced than in allis shad - in adults not more than 30 on the lower arch of the first gill arch. Grows to about 3.5lb. Shoals ascend rivers to spawn, but usually do not travel beyond the head of the tide. A land locked form occurs in the lakes of Killarney. Please Note Allis shad and twaite shad of a similar size are extremely similar in appearance.
Identification is very difficult and has to be carried out by a biologist.
The Irish Specimen Fish Committee requires that fish be identified by a biologist nominated by the Committee.