World Ocean Census - Extract 5 - In quest of a zero-year baseline
13 December 2010
Fifth amazing extract from The World Ocean Census: A global survey of marine life: Painting a Picture of the past - In quest of a zero-year baseline.
Another Census investigation is using direct sources of evidence – ancient fish bones from archeological digs – to identify the earliest human impacts on abundant marine species, with the goal of setting a “year zero” for shifting baseline studies. Protein from fish bones recovered from archeological digs is providing insight into the fishing practices of civilizations of long ago. As James Barrett, head of the fish-bones project at the University of Cambridge, explains, “One of our main objectives is to chart the ebb and flow of fishing, using bones from archeological sites.” The scientists’ ultimate goal is to figure out if they can accurately define how long humans have been influencing marine ecosystems in northern and western Europe. The work raises many questions, including how far back one should go and what scale should be studied in order to find the origin of a given fishery. Basic questions such as what species were being fished, who was fishing, when and where they were fishing and for what market also pose many challenges to creating an accurate history of fishing practices long since past.
To add to the information provided through analysis of what fish were caught and traded, scientists turned to the exacting process of measuring stable isotopes in the fish-bone protein (isotopes are naturally occurring forms of the same element that have different numbers of neutrons in their atomic nuclei). Protein survives in bones even after thousands of years, so ancient fish bones can tell us what the fish ate and what ate them; scientists call this their trophic history. Since the bigger fish at the top of the food web carry a different isotopic signature than the smaller ones below, the characteristics of protein present in a fish bone allows scientists to determine where the fish fell in the food web.
James Barrett and his team of researchers are using these techniques to explore when various societies “fished down” the food web, where the fish were caught and whether early eutrophication might have occurred. By learning how people fished in the past, scientists hope to arrive at a better understanding of both natural ecosystem fluctuations and human-induced changes in specific regions.
Text and images reprinted with permission from World Ocean Census: A Global Survey of Marine Life by Darlene Trew Crist, Gail Scowcroft and James M. Harding Jr., Firefly Books, 2009.
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