I was encountering the same thing. For Ehll Tou's collectables, the description of the fish gives literally ZERO useful information. Fatty herring, for example.

"in a blind taste test, three out of four people cannot tell the difference between fatty herring steak and antelope steak"

That's it. That's all you have to go on. How are we supposed to try and find out where these fish are without using external sources?