A Japanese bidder has bought a single bluefin tuna for a record price of $1.7 million (155m yen) in an auction held at Tokyo's Tsukiji fish market.

Kiyoshi Kimura, president of Kiyomura Co. which owns a chain of Sushi-Zanmai restaurants, bought the fish for three times the previous record price set last year. Kimura was the buyer of the bluefin tuna last year too.

Kimura himself agreed that this year's price for the fish was a bit expensive, but wanted to encourage Japan with his bid.

"I wanted to meet expectations of my customers who said they wanted to eat Japan's best tuna again this year," Kimura told Jiji Press.

"With this good tuna, I hope to help cheer up Japan."

The fish, weighing at 489lbs, was caught off north-eastern Japan. The auction was held amid growing concerns over the population decline of the valuable species, as a result of overfishing.

Nearly 80 percent of the fish species caught worldwide is shipped to Japan for consumption. Bluefin tuna's red meat is used in sushi, a popular Japanese dish. The fish would cost around $3,603 per pound.

According to United Nations Food and Agriculture Organization, the Japanese consume 128 pounds of fish per capita every year, as against the global average of 37.6 pounds of fish consumption, reports Bloomberg.

Environmentalists have continually raised concerns about the dwindling population of the bluefin tunas that are of three different species - the Pacific, Southern and Atlantic bluefin tuna fish.

An intergovernmental group is all set to release data about the population of the Pacific Bluefin tuna Monday. Environmentalists believe it will likely reveal that the fish is facing an alarming decline.