Every year, tuna hauled in at the small town of Oma in Aomori Prefecture, dubbed "black diamonds" for their value and color, make headlines as they fetch millions of yen at the Tsukiji fish market auction at the start of the year.

This year, a 212-kg Oma maguro (tuna) fetched ¥74.2 million ($650,000) — the second-highest price on record. Other Oma brand tuna have also sold for several million yen each, including one that fetched an all-time high ¥155.40 million in 2013.

Fishermen from towns other than Oma also catch tuna in the Tsugaru Strait.