..... would it not be reasonable to suggest that until the main reason they congregate around the Ythan estuary is present in sufficient numbers (that would be sea trout & salmon) to prey on, seals will move elsewhere to find food.
Therefore, spotting them around the estuary at the moment is perhaps less certain than it will be in (perhaps) 3 months time ???
I saw plenty of them in the estuary when I fished there....... and I can recall when I lived on Ardnamurchan the old skipper I started working with never set his salmon bag nets until the seal populations movements 'told him to'.
H