White tuna is one of the companion fish of tuna, also called aromatic oil fish, oil sweetfish. It has a flavorful and tender taste, rich in fish oil, and is one of the most valuable fish species in Japanese cuisine.

Distribution: White marlin used to be a ubiquitous species in the Atlantic Ocean, however, due to overfishing by fishing enthusiasts, the U.S. National Marine Fisheries Service has recently mandated that no more than 250 Atlantic blue marlin and white marlin can be caught per person per year. Despite these measures, the number of white marlin in existence is only 12 percent of what is needed to maintain the base catch, according to a 2002 estimate by the International Association for the Conservation of Atlantic Tunas.

NOW: For a prized game fish, a single identity mix-up could be fatal. A new study reveals striking similarities between roundscale sailfish and white marlin, which means the latter - an already endangered species - is likely closer to extinction than previously estimated.

RELATED:Today there is reason to believe that this worrisome statistic may still be too optimistic. When a team of oceanographers attempted to classify round-scaled sailfish, the researchers found that they shared many similarities with white marlin. Scientists first identified the round-scaled sailfish 170 years ago, while Mahmood Shivji, an oceanographer at the Guy Harvey Research Institute in Fort Lauderdale, Florida, USA, and colleagues made the first attempt to fully analyze the species. Deoxyribonucleic acid (DNA) tests showed that the round-scaled sailfish is a distinct species among billfish - including Mediterranean sailfish, marlin, and white and blue marlin. However, if judged on appearance alone, the round-scaled sailfish is almost identical to the white marlin, except for its scales, which are a bit rounder.