But instead, some fish they’ve surveyed have only about a third of the fat content of healthy fish of the same age and length. They look gaunt and like they’ve been stretched thin. Some also have deformed spines.
I mean...
I got a pretty good guess what would be fucking up the spines of fish living significantly deeper than they normally do...
But animals move into new niches before they adapt to those conditions.
The "best zombies" will survive down there, and their genes that help them, will get consolidated overtime. Eventually to the point they differentiate to a sub species or even new species.
It's very likely we're just seeing the first steps of evolution. Eventually their spines will be able to handle it, and they're adapt to get enough calories down there or shrink in size...
Or they never adapt and generations keep trying and dying.
But statistically. Eventually. It'll happen
Quick edit:
There will also be gene transfer from zombies back to normal group at first.
So we will likely see weird shit in the main population until zombies are able to always stay deep. Even then there's u likely to be a clean break between populations