fish wont spawn naturally

there are no fish spawning in my world. there are dolphins, squid and drowns but there are no fish. there use to be fish but now when u swim around on the whole map you cannot find any.

I do have several mods installed on my realm but even if I remove them no fish will spawn. 

if I create a new world there are fish but not on my realm and not on the copy even with all the mods off.