After some time of doing other things on the server I returned to that river and no matter how much I walked around, what I did or even if I restarted the server it always had a maximum of 5 Goldeens/Magikarps in it's whole length.
Does anyone know what could have caused the abnormally low spawn rates? I have also found about 3 other fairly long rivers, all showing the same low spawn rates. I know I shouldn't be expecting Dratinis and Dragonairs all over the place but there aren't even any Magikarps to begin with.
I thank anyone eager to help in advance.