cod uncontrollably spawning in natural and player made water sources

Cod uncontrollably spawning in natural and player-made water sources.

Can be used as an infinite food source.

What I expected to happen was...:
Nothing.

What actually happened was...:
Cod started spawning.

Steps to Reproduce:
I sadly do not know a specific trigger because it does not seem to always trigger, so I think it has something to do with how far it flows straight down.