It seems my earlier report that the shad at John Yi's were harvested from Southern U.S. rivers was mistaken. According to the signs, these comes from European waters. Further research shows that there are two species of European shad inhabiting eastern Atlantic waters from Morrocco north to Norway, though the commercial shad fishery is centered in the Gironde-Garonne-Dordogne basin of France.
Although these fillets, whole fish and roe sets looked fine, you're probably better off waiting for the local run, which arrives in late April and early May. Or visit the annual Lambertville shad festival, scheduled this year for April 25 and 26.