I am about 90% sure those are big heads and not silvers. I still havnt confirmed 100% a silver at the falls yet though Ive thought Ive seen them at a distance. They are hard to tell apart up close, even harder at a distance though.

The easiest way is that a silver wil have an arc shaped belly called a keel that comes to a point their bodies are kind of like a knife blade in cross section. Big Heads have flat bellies and tend to be darker.

Despite being a horrible fish, that is one fantastic photo!