Really addictive game, this has pretty good potential now that you're planning to make it into a full version!
Obviously as others have pointed out, there are issues with lag (especially in regards to audio) and balancing in terms of the amount of money obtained.
Also in my opinion the creatures should scale repeatedly (felt a bit easy when it went from feeding a kraken/mermaid back to a turtle again)
Could do with buttons to switch between fish (like a hotbar maybe) as 1. It felt less smooth having to click a settings thing then another to switch to the next fish when that could be a button, and 2. The worst part was catching something like a sunfish and then due to the order, it ends up being used on a turtle rather than a mermaid for example.
Other than that, this is a game that I (and many others clearly!) could find themselves playing for hours! Great game, especially given the time constraints!