This game needs some instructions! It's nicely relaxing, and does feel like fishing, only there's no instructions on how to cast (swipe? Press lever? Touch rod?), nor how to reel once you've caught a fish! Only vague info on fighting a caught fish.
I really appreciate the feedback. I tried to be clever and place instructions in the gameplay itself (it plays during your first play (once per boot-up), if the correct controls aren't put in within the right timelimit, but I guess it's still too vague.)
The fight controls are: Swipe up,down,left, to fight the fish (and raise the fight bar on the left) -- when the reel handle starts spinning quickly tap it several times to stop the spinning. (The fight bar on the right will drain faster if you don't.) Undocumented tip: if you can keep the fish on the reel for around 24 seconds the fish will become 1/3 weaker, which will help in the final battles with the gold lure fish.
Here is a little demo video of the game, I hope it clears up some control confusion: