For decades fish were considered incapable of pain due to their simpler brains. A revolution in fish neuroscience has overturned this assumption and begun to reshape welfare legislation.
If fish experience pain — as the evidence increasingly suggests — then recreational catch-and-release, live bait fishing, impalement, and suffocation during slaughter all cause suffering. The welfare implications are enormous given that approximately 1-2 trillion fish are killed commercially each year with essentially no welfare consideration.