Is shellfish aquaculture considered a wrong livelihood?

I am currently employed on an aquaculture farm that specializes in clams and oysters. According to our modern system of taxonomy, both of these organisms are considered animals. I also know that a profession in which one trades animals is not right livelihood. However, according to this site , clams and oysters don't really have brains. Furthermore, according to wikipedia , it would seem that the nervous system of the mollusk doesn't really function to sense pleasure or pain. So, I am wondering- does trade in shellfish count as wrong livelihood? If so, how does one determine what is an animal and what is not according to Buddhism? If one is meant to go by whatever their respective society defines as an animal, surely this definition will change and therefore make this aspect of right livelihood unreliable, right? Thankya