Yea. I agree with you Tom. This does not make any since at all. I too had fish in an aquarium and a pond and realized later that they were not spawning anymore in the oceans. I guess until more complaints are made, the "Mods" are not going to do anything about it.
The answer to this issue is don't release any fish from a bucket unless you use less then 15 of them. Anymore than that will stop all spawning of animals in the oceans. This includes dolphins, squid and fish. Apparently this is " Works as Intended".
So... 16 released fish in a bucket in a freshly generated world that stops all ocean mobs from spawning is as intended. Sound like a bug to me. Very frustrating and should not be a feature if that is the case.
Thanks Torabi for looking into this.
I too did not think they were supposed to count towards the mob count. I thought they were considered a named mob. I started naming the fish in a bucket at first, which gives the same results btw, then I did them without naming them as the wiki states that you do not need too.