I understand "to" as meaning "in the direction of" or "towards". It's not common, but it can work.
"Fishes" is an odd one. You can say "fishes" to mean "different kinds of fish", but it also has a poetic or biblical feel. You're right that "fish" is the standard plural. Interesting story behind that one.
I wonder if the text you are reading has these forms to deliberately give a poetic feel.