I love this idea a lot! I think the fishing minigame is implemented very well and is a very relaxing experience, and I got strangely excited by the fact the water was waving? It's a cute little detail that wasn't necessary but adds a lot to the experience.
I think, for a prototype, the game is very in depth! I'm a big fan of the names you gave the fish and the idea of the fishing journal. I can tell a lot of thought went into this!
Since you're continuing to develop it more, I would love to see more of a story as to why these aliens are invading and why our player character and the fish are the only ones who can save the world. It seems very silly in the best way possible and I am intrigued to learn more. I'd also say one very minor thing: volume settings would be amazing. When a fish first bit my lure, the sound genuinely jumpscared me!
Excited to see what comes next! If you get a chance to, I'd love for you to send it over to me when it's next updated/when it's done!