Here in SA, there is a short season where one is allowed to catch Shad, because of over-fishing. When the Shad bite, it's called a shad run as they bite as soon as the fisherman's line is in the water, it's quite a sight! They cannot be sold here either. It's one of the tastiest fish I've eaten!
Quoted from this link: https://wwfsassi.co.za/fish-detail/40/
Elf or shad, (Pomatomus saltatrix) are relatively fast growing, migratory, schooling fish that are widely distributed around the world in both subtropical and warm-temperate continental waters. They appear fairly resilient to fishing, however, due to their popularity as a gamefish and their high catchability, they have been heavily fished.