In this Sept. 12, 2005, file photo, John Petraborg holds up a 35-pound moonfish, also known as opah and normally found in the deep waters near Hawaii, on board his troller Roulette at ANB Harbor in Sitka, Alaska. Scientists have identified three new species of opah, a colorful peculiar deep-diving fish that is increasingly caught and served in U.S. restaurants. A team of researchers with NOAA Fisheries has identified five distinct species of opah, rather than just one. (James Poulson/The Daily Sitka Sentinel via AP)
SEATTLE — The fish buyer noticed something different about the large, colorful disc-shaped opah waiting to be sold at the auction house in Honolulu. Among the differences: one fish had a bigger eye than the other.