I wanted to make this thread because I ended up spending 4 hours trying to catch a single fish because I didn't know where to start.

The saddled birchir despite saying on its wiki guide that it is bigger than a black bass, is not. It is near if exactly the same size but a little bit fatter in shape. The wikia says it is evenly spread from 9pm - 4am, I spent 4 hours from 12am - 4am looking without a single hint. I log out time travel back 6 hours and literally the FIRST FISH I catch is the saddled birchir. Could just be luck but I would strongly recommend trying 9pm - 12am if you are struggling to catch this demon.

Thanks
Oversal

Congrats on getting one.  
Not sure why it's says that on Wikipedia.
I use http://animalcrossingus.tumblr.com/guides for the where, when, weather and only in your own town.
Completed 11 bug collections and 25 fishing collections using the guide.

I just went fishing for anything that looked like a black bass.  Walked the full length of the river and back so the fish could spawn again.  Also went in and out of buildings to get different fish to appear.

Found that I caught the arrowana instead of the saddled birchir.