The East Sea is warming at two-to-four times the global ocean rate over 2000–2025, and the once-dominant fishery for the ommastrephid squid Todarodes pacificus around Korea has contracted by more than 90%. Whether warming contributed to that decline cannot be settled from the catch record: catch and catch per unit effort (CPUE) confound abundance with fishing effort, and the strong raw correlation between sea-surface temperatu...