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A U.S. researcher has used historic photographs as evidence of fishing's impact on marine ecosystems and the decline of "trophy fish."

Graduate student researcher Loren McClenachan of the Scripps Institution of Oceanography at the University of California-San Diego accessed archival photographs spanning more than five decades to describe an 88 percent decline in the estimated weight of large predatory fish imaged in black-and-white 1950s sport fishing photos compared with the relatively diminutive catches photographed in modern pictures.

"These results provide evidence of major changes over the last half century and a window into an earlier, less disturbed fish community ..." she said.

McClenachan's said her studies, which involved analyzing approximately 1,275 fish from photographs, are part of an emerging field called historical marine ecology, in which scientists study photographs, archives, news accounts and other records to help understand changes in the ocean ecosystem over time.

McClenachan said she believes historical ecology can not only help describe the structure of ecosystems that existed in the recent past but can be used to establish goals for restoration of large predators, both on land and in the water.

The study is to be published in an upcoming issue of the journal Conservation Biology, while a companion paper will appear in the journal Endangered Species Research.