Bunker 101

I was just wondering about the bunker migration. Were do they start from and were does it end. Do they come into the back bays to spawn? I know they don't spawn in the rivers like the herring and shad. Are the peanut bunker the fry from this years spawn? How long do menhaden live if they are lucky enough to escape the stripers,blues and netters? It seems pretty amasing that they come back so strong every year with all the pressure on them. They really are it seems the most important fish in the sea and probably the most overlooked.