The evidence for pain experience in rainbow trout and how this shapes welfare obligations in trout aquaculture.
The evidence for pain experience in rainbow trout has shifted significantly over the past two decades, from strong skepticism to a scientific consensus that at minimum, fish have welfare-relevant responses to noxious stimuli that deserve moral consideration. The precautionary principle applies clearly: given the evidence for nociception, behavioral responses to pain, and analgesic effectiveness in trout, the burden of proof has shifted to those who would deny welfare consideration rather than those who advocate for it. In aquaculture, the most significant welfare implications are at slaughter — where percussive stunning and electrical stunning cause rapid insensibility, while CO2 and ice slurry cause prolonged distress — and during invasive husbandry procedures. The welfare-progressive approach to trout production treats pain prevention as an obligation rather than an optional enhancement.