Theo -- probably much truth in what you said, especially about the rolling spawn. Back when I worked in Kansas, I spent quite a bit of time on gizzard shad. People told me beforehand that they had two distinct spawns. After working more closely on them, they clearly had an extended spawn and definitely not two separate spawns. The term rolling spawn is a good one. The shad in better condition (higher Wr) spawned first, those in lower condition first had to increase Wr and then they spawned, by then the first fish had ripened their second clutch of eggs and spawned, etc. So, I really like your term.
One key to this is that in some fish species, individual fish have the capability to spawn more than once. If I take the ovaries from a female bluegill or gizzard shad just prior to the spawning period, they have different sizes of eggs in their ovaries. There is a large size of eggs just about to be spawned, a second clutch of smaller eggs that can be ripened for a later spawn, and then some tiny eggs that generally are believed to be for the next year. If I take eggs from a walleye or northern pike just before the spawn, all the eggs are a single size. Single spawners, clearly!
