Sometimes it pays to blow the dust off those old archives. An Italian research team has been able to reconstruct how fish stocks in the Northern Adriatic Sea have changed over the last 200 years thanks to a creative method for transforming the diaries of long-dead naturalists and fishmongers into crunchable data. These long-ignored “eyewitness accounts” reveal sometimes dramatic ecosystem changes, including a major loss of sharks, rays and large fish species.
Scientists trying to understand how fish and other wildlife populations have changed over the last few hundred years often face a serious roadblock: A lack of scientifically-valid numbers from the 18th, 19th and early 20th centuries. As a result, they have no “baseline” against which to compare what they see today. There are, however, some less quantitative sources of information that provide a window into the past. They include things like diaries kept by naturalists, anecdotes included in newspaper stories and ledgers kept by tax officials and business owners. The challenge, however, is converting such qualitative or incomplete information into hard numbers.
To leap that chasm, Tomaso Fortibuoni and colleagues at Italy’s national institutes for oceanography and environmental protection first scoured archives, libraries and museums in Venice, Padua, and other cities for notes and papers describing Adriatic marine life. Among the finds were ledgers from fish markets, and lists of marine life tallied by early naturalists, who sometimes visited fish markets, interviewed fishermen, and even made notes on how the fish were caught. Overall, their haul included 36 naturalists’ books published between 1818 and 1956, and annual market data from 1847 to 2000 for approximately 100 fish species or groups of species. The team then painstakingly sifted the information to evaluate the abundance of 255 species at different times over the last 200 years, ranking each species from “very rare” to “very common,” and using mathematical filters to make the numbers comparable.
The combined data revealed some major trends between 1800 and 2000, they report in PLoS One. Sharks and rays (Chondrichthyes), for instance, became increasingly rare, dropping from 15.9% to 4.6% of the observed fish community. Larger bottom-dwelling species also declined, from 24.4% to 8.5%, as did big-bodied fish in general, from 18.3% to just 5.8%. Late-maturing species – those taking 4 to 6 years to reproduce – slumped from 11.4% to 4.6%. The records also show some species disappeared entirely, including the angel shark (Squatina squatina), the tope shark (Galeorhinus galeus), and sturgeon (Acipenser sturio); all were common until 1950. Although it is difficult to sort out all the factors that have contributed to such declines, the authors conclude that fishing appears to have played a major role.
The study shows the value of “eyewitness accounts of fish species, which have long been disregarded by fishery biologists as being ‘’anecdotal’ and not ‘science,’” the authors argue. In this case, they say, the old records “proved to be a useful tool for extending the analysis into the past, well before the onset of field-based monitoring programs.” – David Malakoff | November 25, 2010
Source: Fortibuoni, T., Libralato, S., Raicevich, S., Giovanardi, O., & Solidoro, C. (2010). Coding Early Naturalists’ Accounts into Long-Term Fish Community Changes in the Adriatic Sea (1800–2000). PLoS ONE, 5 (11) DOI: 10.1371/journal.pone.0015502
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