Capilano River (or smart seagulls again?)

On another one of my bicycle shopping trips (The butcher shop at the western end of old Park Royal has Leberkaese), I cycled over a bridge over the Capilano River and noticed something confusing out of the corner of my eyes.  I wasn't sure whether I had seen seagulls or rocks lining the river bed.




When I came to a stop and looked again, it turned out that it was both !

Could they be patiently waiting for freshly hatched salmon babies that are trying to make it to the ocean?

Safety