In a recent review on the concept of fish welfare, I argue that concern on fish welfare is definitively a genuine matter, and the main challenge is to find valid methodologies to evaluate this internal state in these animals. I also argue in that review that studies on fish preference should be emphasized, instead of frustrated attempts to empirically demonstrate sentience in the non-human animals. From this theoretical background, in the present text I examine more detailed the preference tests, indicating important conditions and restrictions to minimize misunderstanding that could affect interpretation about the state of fish welfare. First, I indicate fish conditions that should be considered to analyze results of preference tests. They are: phylogeny, biological rhythms, ecological conditions, ontogeny, social condition, and individual experience. Then, I discuss methodological conditions and approaches to perform and interpret preference tests, an attempt to improve understanding on what the fish has to tell us about their internal states of welfare.
choice test; fish; preference test; stress; welfare; well-being