When Pixar’s Finding Nemo was released in 2003, it unleashed a tidal wave of demand for the cute orange clownfish, the species that the character Nemo is based on. Sales of clownfish rose as much as 40%, according to some estimates. Some scientists were concerned that the population of the fish would be severely depleted if too many were caught in the wild. Aquarists, however, soon figured out how to breed clownfish in captivity, reducing the impact of lots of them being taken from coral reefs.

Now, scientists are bracing for Nemo’s sequel, Finding Dory, which will be released on June 17. Dory is a blue tang. Unlike the clownfish, scientists and aquarists have not been able to breed the blue tang in captivity so far. That’s led to worries that now this species could face severe pressure from overcollecting on reefs (primarily in the Indo-Pacific, one of the world’s top sources for wild tropical fish), if movie viewers turn out to be as interested in owning pet blue tangs as they were in owning clownfish.

One animal rights group is petitioning the Walt Disney Company to put out a public service announcement asking people not to buy the fish. Their petition cautions, “If Disney does not place an explicit warning at the beginning of the film asking viewers not to adopt Blue Tang like Dory, then we will see a sharp decline in their population.”