The strait where the Inland Sea meets the Pacific runs fast. The water temperature barely shifts, the plankton is abundant, and the current is strong enough that a fish spends its whole life working against it. Mackerel and horse mackerel that come out of that water are noticeably firm, and it is the swimming rather than the feeding that appears to do it.

The waves are high and the seabed is complicated, which rules out nets. So the boats fish with a single line, one fish at a time, and each one is killed on board the moment it comes up. That is not only about freshness; it keeps parasites in the gut from moving into the flesh, which is why this fish can be eaten raw with confidence.

The selling is stranger. Fish are traded by eye, judged for size and weight while still floating in the holding tank, with no scales involved anywhere in the transaction. It is called tsuragai, face-buying. Weighing would bruise them, so the buyers learned instead to weigh by looking.

In 2006 this was the first name entered in the regional collective trademark register. What the registration actually protects is an inconvenience: the refusal to use a net, the refusal to use a scale. Remove those and what is being sold is simply mackerel.