High spawn rates for mobs

Put the summary of the bug you're having here

What I expected to happen was...:
A normal amount of squid and salmon, possibly slightly higher because it was the only river within loaded area

What actually happened was...:
Large amounts that began to lag my game from hundreds of entities

Steps to Reproduce:
1. Go to a fairly isolated river
2. Wait several minutes
3. After some time, the mobs will increase exponentially

Extra comments:
I noticed the same high spawn rates with bats, but I was not able to replicate it