Hi! Thanks for playing our game :)
There's a lot more we wanted to get in before the deadline. I definitely should've focused on getting the core gameplay working properly before setting some of the other stuff up. To catch a fish you just need to click within short time after the bobber dips below the surface and you hear the sound effect. If a fish doesn't get added to your inventory, it's probably because I messed up somewhere. I know there are definitely a few that you can't catch in the version we released a few hours after the deadline, and in the version before the deadline the inventory is completely broken. It was a good learning experience though and I'll definitely revisit the idea some time soon.
I'll give your game a go right now :)