Today, its population is a little more than half of what is was in 1974, when it was already depleted, and experts expect international quotas agreed to last year by the International Commission for the Conservation of Atlantic Tunas (ICCAT), under a rebuilding plan for the species, to bring further decline.

Even under the best management, the stock would have a difficult time recovering, in part because bluefin are slow to grow and reproduce. When they are fished relentlessly, recovery is nearly impossible.

That threat is more severe in the Gulf of Mexico, one of the major areas for the species, where US fishermen using surface longline fishing gear, to target yellowfin tuna and swordfish, also indiscriminately catch and kill more than 80 types of other marine life incidentally, including western bluefin. More than half of all bluefin caught on Gulf longlines die before they are brought to the boat.

Mexico however has officially surpassed its ​whole 2018 quota just by 3 May, Jamie Gibbon, an officer on Pew’s global tuna conservation campaign, was quoted as saying.

As informed earlier, fishery managers have taken an initial step to eliminate proven protections for western Atlantic bluefin tuna in the Gulf of Mexico. The new proposal could abolish conservation-minded requirements governing fishing gear and closure areas during peak spawning periods.

NOAA began to improve protections for spawning bluefin in 2011 by requiring Gulf surface longline fishermen to use thinner, weaker hooks year-round that straighten to release large bluefin before they die of exhaustion on the line. That change has reduced dead discards of bluefin tuna in the Gulf by almost 75%.

In 2015, NOAA added comprehensive management measures that included establishing two new Gulf of Mexico gear restricted areas (GRAs) totaling nearly 27,000 square miles in which the use of surface longlines is prohibited during peak bluefin spawning in April and May. Since the GRAs took effect, the average annual number of bluefin hooked on longline gear has declined by 82% during closure periods, proving that the measures work.

Pew has also singled out Japan for exceeding its limit for tuna fishery, as the country's authorities raised the quota for 14 prefectures last May, although they had already exceeded their annual limit.