The shrimp welfare project

Shrimp do not have experience. There is no place within the shrimp, no anatomical structure, where experience can reside. The article, and many of the articles it links to, confuse the existence of pain receptors, complexity of behavior, memory, aversion, intelligence, learning capacity, and other measures for experience.

Since they don’t have experience, they can’t suffer, in the morally relevant sense for this argument.

What about the brain? https://link.springer.com/article/10.1007/s00441-017-2607-y#...

As is most clear in Figure 8 of the article you refer to (which is good science, but mainly of interest to specialists in the neural/sensory anatomy of certain classes of animals), the shrimp lacks, among other features, a cortex and a thalamus. These are known to be necessary for the generation of conscious experience.