The incredible shrinkingtrophy fish

Trophy fish (at left) caught on Key West charter boats: a) 1957, b) early 1980s and c) 2007.


From a news release issued by Scripps Institution of Oceanography:

A unique study by a scientist at Scripps Institution of Oceanography at UC San Diego has provided fresh evidence of fishing's impact on marine ecosystems. Scripps Oceanography graduate student researcher Loren McClenachan accessed archival photographs spanning more than five decades to analyze and calculate a drastic decline of so-called "trophy fish" caught around coral reefs surrounding Key West, Florida.

In a paper published online in January and printed in an upcoming issue of the journal Conservation Biology, McClenachan describes a stark 88 percent decline in the estimated weight of large predatory fish imaged in black-and-white 1950s sport fishing photos compared to the relatively diminutive catches photographed in modern pictures. In a companion paper being published in the Endangered Species Research journal, McClenachan employs similar methods to document the decline of the globally endangered goliath grouper fish.

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

McClenachan's studies 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 and establish baselines for future ecosystem restoration.

McClenachan believes that 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.

While conducting research for her doctoral thesis on coral reef ecosystems of the Florida Keys, McClenachan came across what she describes as a gold mine of photographic data at the Monroe County Library in Key West. Hundreds of archived photographs, snapped by professional photographer Charles Anderson and others, depict sport fishing passengers posing next to a hanging board used to determine the largest "trophy fish" catches of the day. All of the photographs document sport fishing trips targeting coral reef fishes around the Florida Keys. McClenachan supplemented the study with her own photographs and observations on sport fishing trips in 2007.

In all, she measured and analyzed some 1,275 fish from photographs.