the names of plants and animals surely wouldn't be the same as we have
Required reading: https://tvtropes.org/pmwiki/pmwiki.php/Main/TranslationConvention
Should a salmon-like fish simply be called a salmon, or should I come up with a new word for it?
Required reading: http://tvtropes.org/pmwiki/pmwiki.php/Main/CallARabbitASmeerp
Beyond that, I don't think we can give you any answers that aren't overly squishy.
FWIW, the story I'm writing has much the same problem. My preference is to generally ignore it (i.e. Translation Convention fully in force) unless I have a really good (possibly plot related) reason.
I recall reading somewhere recently that Star Wars wouldn't talk about "the galaxy" because the word "galaxy" derives from the Latin for "milky way"... but that's completely stupid because of Translation Convention. Obviously the word in Star Wars' common tongue wouldn't be the English word "galaxy", but if they have a word, then, per Translation Convention, that word would be rendered as "galaxy" when presenting the story in English.
The same can go for "salmon". If you have a fish that is actually a salmon, then it's perfectly reasonable to just call it "salmon". If it's similar to a salmon, but actually something different, then it's reasonable to either call it something different, or call out that, while you (the narrator) are using "salmon" so as to not confuse readers, it's actually something else. (Or you can be lazy and use "near-salmon", with a similar explanation.)
I also need to add, there's a reason for the aforementioned tropes. Namely, if your objective is to tell a story¹, you don't want to confuse your readers more than necessary.
(¹ This is admittedly an assumption. If you are instead writing something like an in-universe encyclopedia, or anything really that leans toward world-building for its own sake, then this argument may not apply.)