Tricky to learn, but I eventually figured out how to catch creatures on my own. Interesting concept, though there is room for polish in the gameplay aspect (e.g. allow using the same symbol in quick succession) and general communication (the fish-catching animation after going back to the overworld was quite inconsistent, so I wasn't even sure if I caught the fish or not).
I liked the general atmosphere and a variety of environment, even this not directly relevant to the gameplay - it really added life to the game. One potentially nice addition - have the background change between zones gradually (e.g. using merge_color) rather than abruptly. Overall, I managed to find 3 clues and all four fish and completed the game. Nicely done. ^^