Anyway:
- Orcas are mammals and not fish.
- Your study talks about fish. So does the first article I mentioned. "My" article mentions nociceptors and opioids (pain killers) and an experiment with painkiller lidocaine that suggests that fish feel some kind of pain. Note that both fish and mammals have nociceptors and opioids as chemicals in the brain. That fishes eat after surgery does not mean that fishes do not feel pain. Some people eat as response to stress and fear.
Quote from "my" article (I guess finfish means true fish in this context): In 2013, the American Veterinary Medical Association published new guidelines for the euthanasia of animals, which included the following statements: “Suggestions that finfish responses to pain merely represent simple reflexes have been refuted. … the preponderance of accumulated evidence supports the position that finfish should be accorded the same considerations as terrestrial vertebrates in regard to relief from pain.” Read more: https://www.smithsonianmag.com/science-nature/fish-feel-pain... Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv Follow us: @SmithsonianMag on Twitter