It's already been established that a sense of smell is vital in Salmon's ability to return to the headwaters of their birth. I'm not aware of any "genetic" component, it is simply that Salmon remember the smell of where they were born and most salmon try and return. The feat is amazing and there are many "instinctual" behaviors involved, but no evidence that there is a genetic heritage from a specific headwaters is important in returning to that headwaters.

This "genetic memory" talk is just uninformed people jumping to conclusions and spreading speculation as fact.

I’m merely proposing a mechanism for how it could be possible to have salmon return to the same spot after several generations, if that actually does happen.

The idea would be that a salmon could be genetically predisposed to follow a certain path, perhaps preferring the smell of a certain combination of chemicals, thus encoding the location. It means the „memory“ would be encoded via genetics as a result of genetic combination and mutations, and the „encoding“ would essentially just be selection. It’s just speculation on how this genetic memory idea could work without actually encoding memories on genes.