LOS ANGELES -- Ransom A. Myers, a former government scientist who sought to warn that overfishing would lead to collapse of Atlantic cod populations and later discovered that 90 percent of the world's bluefin tuna and other large predatory fish had disappeared, has died. He was 54.
Dr. Myers died Tuesday in Halifax, Nova Scotia, of complications of brain cancer, according to colleagues at Dalhousie University, where he was a professor of ocean studies. He was diagnosed with an inoperable brain tumor in November.
Dr. Myers was a gifted mathematician and biologist who shook up the insular world of fisheries science with blunt statements about how various species of sharks, turtles, and fish were headed toward extinction if industrial fishing did not retreat from excessive hunting.
"Humans have always been very good at killing big animals," Dr. Myers said. "Ten thousand years ago, with just some pointed sticks, humans managed to wipe out the woolly mammoth, saber tooth tigers, mastodons, and giant vampire bats. The same could happen in the oceans."
Such pronouncements did not spring from preconceived ideology, but rather from patterns he discerned from fishing records, scientific surveys, and other data he collected. Several of his studies focused on Georges Bank, a key fishing ground for fleets from New England.
Dr. Myers had a unique ability to look at complex global changes and pick out trends that others had had missed, said Boris Worm, a colleague at Dalhousie. "Unlike most scientists who look at a snippet of reality, he believed we are facing global problems that need to be analyzed on a global scale and communicated on a global scale," Worm said.
With the help of Worm, Dr. Myers spent years poring over five decades of Japanese logbooks and other fishing records to determine that 90 percent of the world's sharks, tuna, swordfish, cod, and other big predatory fish had been stripped from the seas by industrialized fishing since the early 1950s.
The results, published in 2003 in the journal Nature, stirred scientific debate that continues to roil, even though a review panel by the National Academy of Sciences has upheld its conclusions.
"We confirmed that the pattern was right," said Andy Rosenberg, a panel member and longtime colleague now at the University of New Hampshire. "Most people criticizing the methodology didn't like the answer."
Dr. Myers's plain-spoken style got him into trouble in the 1990s, when he began to condemn the Canadian government's handling of Atlantic cod fishery, even though he worked for Canada's Department of Fisheries and Oceans.
The department tried to squelch his papers explaining that excessive harvesting was responsible for the 1992 collapse of Atlantic cod. The government has blamed everything from voracious seals to changes in water temperature for the decline. Later proven right, Dr. Myers recounted the censorship and other obfuscations that went on within the Canadian government that forced him to flee for the academic freedom of Dalhousie.
Dr. Myers believed strongly that information collected at taxpayers' expense should be made public. He posted his data on websites and invited interested parties to try to pick apart his analysis, believing this was science's pathway to the truth.
In October 2005, Fortune Magazine declared him one of the top 10 people to watch in the world, listing him between Senator Barack Obama, Democrat of Illinois, and the cofounders of Google.
Born and raised in Lula, Miss., Ransom Aldrich Myers Jr. was one of four children and the namesake son of cotton farmer who owned a plantation stretching across thousands of acres. At age 16, he won an international science fair with an "X-ray crystallograph" that measured the symmetry between atoms, a delicate instrument he built in his bedroom.
Massachusetts Institute of Technology tried to recruit Dr. Myers for its physics department, but his father wouldn't stand for it. "My father wouldn't let him go because it was north of Mason-Dixon line," said Susan G. Myers, his younger sister, explaining roots that included ancestors who were Confederate soldiers.
Dr. Myers earned a physics degree at Rice University in Houston and then worked in the oilfields of Kuwait as a physicist before departing on a series of adventures that took him trekking in Nepal, backpacking through Africa, and finally sailing across the Atlantic from African to the Caribbean in a 28-foot boat.
It was during this time that he became interested in fish, his sister said. Dr. Myers published prolifically in scientific journals to the very end, including a paper on sharks that will appear in Friday's edition of the journal Science.