Birds can drop fish after they've captured them. Not longer than a year now, we were visiting my wife's family, and me and my father in law got to Walmart there was a dead fish in the front, but when we mentioned it to my wife who got there before us (separate cars) she said it was struggling for life when they saw it, I don't think there was a lake nearby enough, but I wouldn't be surprised if birds have accidentally introduced life into new bodies of water.
More likely is that birds move fish between bodies of water because of fish eggs they carry on their bodies. This is how most bodies of water become supremely populated in Texas. In Texas all ground water sources, other than 1 lake on the far east side, are created by people in recent decades and almost all of these bodies are full of fish that did not get there on their own.
I once found a recently-dead minnow in the outfield where I was playing software. That was a weird one.
Yeah, but at least two live fish (a male and female) being dropped into the same remote lake, then finding each other at spawning time seems increasing implausible. Never say never, but ...
Apparently some fish species do have small sticky eggs that can stick to the legs of water fowl, or even (with very small probability) pass through them intact, so this seems much more likely. Maybe a group of ducks feeding in one place then flying off to another?