This is an awesome spin on Snake! Kind of the perfect level of difficulty, too - very engaging. I love the music! Is your code available anywhere? GitHub perhaps? I'd love to check it out!
Not sure I have any specific feedback, it's very well put together! If anything, one suggestion for further development could be to have different kinds of food that allow you to temporarily pass through the fish, increasing the spawn-rate of the fish food, etc. Basically varying up the gameplay. But those are just suggestions and what you have here is a very well-functioning, engaging game. Nice work!