We can put a man on the moon, but we can't fire fish over a dam in an enormous salmon cannon and...oh, wait, we can do that.
This is quite literally a cannon for salmon. Just say that name a few times, test it out, see how it sounds like caramel dipping off the end of your tongue. Salmon cannon. Salmon cannon. Best part is that it's a real thing. The fish are loaded just like artillery shells, then whoosh, off they go at 22mp. It can fire 40 rounds per minute. 40 salmon.
There's a point to it all: humanity has dropped stuff like dam walls in the middle of routes salmon need to use to get upstream. So it's humanity's responsibility to come up with things like salmon cannons to help them get where they need to go.