Wednesday, March 18, 2009

If a picture is worth a thousand words, a series of photographs reviewed by one scientist tells an alarming tale of how some of the Florida Keys largest reef fishes are not as big, or abundant, as they used to be.

Most of the data modern-day fishery managers rely on to measure Florida Keys reef fish stocks did not exist before 1979. However, vintage black and white photographs hanging on the wall of many Keys restaurants show fishermen posing with 200-pound Goliath groupers, sawfish and other large species now protected by state and federal laws. Most of the photos studied were taken in the late 1950s and 1960s by Keys photographer Charles Anderson.

Scripps Institution of Oceanography scientist Loren McClenachan took Anderson's photos and combined them with her own to document how the size of the larger reef fish have shrunk during the past 50 years. She compared 13 groups of trophy reef fish, representing some 865 individual types, caught by recreational anglers on head boats, which can carry up to 75 passengers on day trips. The photographs were taken in Key West from 1956 to 2007.

McClenachan was in the Keys in 2007 conducting research for her doctoral thesis on coral reef ecosystems and man's impact on them when she came across the photos in the Monroe County Library in Key West. The photographs were taken of fish caught on head boats from 1956 to 1985. To obtain a current snapshot for comparison, she took similar photographs of fish caught on Key West head boats in 2007.

The mean fish size had declined from about 44 pounds to 5 pounds, and there was a major shift in species caught. Landings from 1956 to 1960 were dominated by large groupers, including Goliath groupers and large predatory fish. In contrast, landings in 2007 were composed of small snappers. The average length of sharks declined by more than 50 percent over the 50 years.

"Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product," McClenachan wrote in her study.

The abundance of fish caught also declined, according to the study. Of the 16 individual sharks caught and photographed between 1956 and 1960, four were hammerhead and three were great white sharks. Between 1965 and 1979, only one hammerhead and one great white shark were photographed, she said. The most commonly caught species between 1965 and 1979 were reef and silky sharks. In 2007, the only species of sharks caught and photographed were immature Atlantic sharpnose sharks.

Marine biologist Jerry Ault, who regularly conducts grouper, snapper, tarpon and bonefish population surveys in the Keys, said McClenachan's study puts a face -- or at least a set of gills -- on a problem. McClenachan's work and Ault's compliment each other, as she is seeing what is making it to the docks and he is surveying the fish in the water, said Ault, a professor of marine biology and fisheries at the University of Miami and director of the Bonefish and Tarpon Research Center.

"It's pretty touchy feely, but it confirms what theories are telling us," said Ault, whose work was cited in McClenachan's study. "It is a good thing because you are making people aware."

McClenachan's work is part of a growing scientific field called historical marine ecology. Marine biologists and ecologists review and analyze photographs, shipping records, historic news accounts and other public and private records to help understand changes in the ocean ecosystem over time, and establish baselines for future ecosystem restoration.

McClenachan's and Ault's work come at a time when fishery managers are struggling to find the best way to keep fish stocks, especially grouper and snapper, healthy and sustainable, while at the same time, not running fishermen out of business. Recent proposed rules call for seasonal closures, smaller bag limits and annual quotas.

Ault estimated the current black grouper population is about 1 percent to 5 percent of its historical size. He estimated that, in the 1930s, the average black grouper landed was about 41 inches and 43 pounds. Today, the average harvested is about 28 inches and 13 to 18 pounds, he said.

tohara@keysnews.com