Similar to MC-134696 but I was told to create a new issue.

The bug

Cods can rapidly spawn and despawn. They don't respect their cap. This can cause 400+ cods to spawn, dropping the server performance. 

This happens more regularly when moving into unloaded chunks, but this is not always required. After a minute the numbers go back down. I printed the number of cods in chat every 10 seconds and attached a screenshot with the results. 

How to reproduce

1. Load chunks near an ocean where cods spawn.
2. Cods should start spawning immediately.
3. /execute if entity @e[type=cod] shows how many cods are loaded. In my testing this could be as high as 500 entities.
4. Notice the server performance has dropped significantly.