The question of whether fish feel pain is muddied by anthropomorphic thinking. Comparing biological phenomena in two species should be informed by the criteria for good animal models: face validity, construct validity and predictive validity. Viewed through this lens, we argue that fish do feel pain and may possess some level of sentience. Evolutionary relatedness, hence similarities and differences between species (fish and humans in this case), are not about black vs. white but about shades of grey
