Smelt/Silversides. Although not as good as live anchovies, 3-6-inch long smelt, are actually the main “live bait” used by most halibut fisherman in SoCal and the Bay Area. Small topsmelt, Atherinops affinis, and jacksmelt, Atherinopsis californiensis are the two species of “smelt” used although neither is actually a true smelt; both are actually members of the silversides family. Typically they are caught by net or Sabiki’ed up via a bait rig.
In southern California the small smelt will tempt bass, croaker (occasionally), halibut, and sharks and rays (especially guitarfish). In San Francisco Bay they mainly tempt halibut, striped bass, sharks and rays. An advantage of smelt is that they are fairly hardy and will stay alive on a hook for some time, certainly far longer than anchovies, but live ‘chovies will almost always out fish them. For frozen smelt simply fish as you would any cut bait.
Typically they are used with a Carolina rig and fished on the bottom although some use them with halibut rigs (sinker on the bottom with a leader a couple of feet up the line) and I’ve seem them used with a sliding leader when fishing for mid-water and top-water fish.
One more silverside should be mentioned—grunion. During grunion runs in SoCal halibut and bat rays often show up in numbers to feast on the small grunion. In response, many an angler has learned that grunion make good bait. They are fished the same as the topsmelt and jacksmelt.