How far to fry travel once in esturaries


My other car is a fly rod.
How far do the pink and chum travel once in the esturaries? In other words, as a beach flyfisher, how close do I need to fish to be the esturaries to fish the fry migrations? If I'm fishing around Mukileo, say, which is between rivers, should I think about heading north or south closer to the river mouths? Or do the fry start moving up and down the beaches for a few miles?
Eventually the salmon smolt will follow the beach down past Mukilteo and beyond. If you're impatient, head closer to the river mouths.