Satire needs a target to actually be satire. Something can be silly, lighthearted, or humorous without being satire. On the flip side, satire itself doesn't actually need to be funny to be effective satire.

So for your example, what is the dead salmon study satirizing? Is there some other study that did something similar that they're making fun of? Is there a broader scientific movement that they're criticizing?

I concede that there may be a target that I'm not aware of. But I find it more likely that someone just said "what if we put a dead fish in an fMRI", and their colleagues found it funny enough to actually do. Many scientists have a sense of humor, and will absolutely do something just because they think it would be funny.