Is there types of fish they just can't eat, or do they need skills to eat them. I have a ww pair, and they won't eat raw Anchory. Also, how do you cook it, if that's the only problem.

Yes, some type of fish are considered "too exotic" to be eaten raw by Werewolves.
I took a look into Fishing.XML (0x90142107481DE889) and to make a fish edible raw a line must be present: < EdibleRawAnimation>something< /EdibleRawAnimation>.

So you could technically make all types of fish edible that way!

Looks like the fish that can't be eaten raw by default are:

But I think you can cook/grill any fish using the fire pit.
And I suppose some can be used in recipes if you place them in the fridge.

I can guarantee that minnows, Kissing Gourami, and anchovies have been used by sims to make sushi. They can even be cooked from the personal inventory if you forgot to put them in a fishbowl.

And Deathfish is half of the ingredients for Ambrosia.

(Although I think I would have serious questions for a werewolf who wants to eat a sea sludge raw. )

Thank you for the answers!