"Do you like ducks?"
Translation:Aimez-vous les canards ?
Using "des" would mean "some" ducks (partitive), some number of ducks. When you are referring a generalization or category of things you use the definite article, in this case "les". The way I think of it, in english, could you add "some" and the sentence would make sense, if so, you can use du, de la, d l', or des ... otherwise use something else like la, le, les.
"des" does mean some, but we're not talking about some ducks. When I ask if you like ducks, I'm usually not saying, do you like some ducks but not others? Rather, I'm asking if you like ducks in general. Do you like (all) ducks? Do you like (the concept of) ducks?
In French, that takes on "les" - Aimes-tu LES canards?
Think of it like a subject: I would never say, do you like some biology? I might say, do you like some aspects of biology and not others? But if I ask you, do you like biology? You know I'm talking about THE subject. Likewise, in French, "aimes-tu la biologie?"
If I want to talk about specific ducks, I would use ce or ces - do you like THIS duck? Do you like THESE ducks? Even in English, we wouldn't usually say the ducks, unless they were ducks in a specific context, and again, you can think about them as an idea:
i.e. "aimes-tu les canards au parc?" "Do you like the ducks in the park?" (do you like the concept of/all the ducks in the park?)