A recent study shows that simply measuring the parts of a fish is a more reliable tracer of its origins than more sophisticated scientific techniques.
The study, conducted by scientists connected with the Smithsonian's National Museum for Natural History, from Stanford University, Manchester Metropolitan University, the British Geological Survey and the conservation organization Rare Inc., was published in July in the Journal of Applied Ecology.
The focus of the study was the Caribbean yellowtail snapper, an important Caribbean fish species that is routinely caught by artisanal fishers. The study sought to identify a practical, cost-efficient tool that would aid in small-scale fisheries management, by helping “to understand the importance of different fishing grounds to local communities and to identify overfished areas that need time to recover,” an article in Science Direct said.
“Small-scale fisheries feed and employ millions of people around the world. Individually, these fisheries remove modest amounts of fish from the ocean, and they are not usually as closely managed as industrial vessels. Cumulatively, however, their impact on the oceans is profound. In 2010, for example, artisanal fisheries in Honduras caught nearly 10,000 metric tons of fish -- more than twice the catch of industrial fleets in the same country,” according to the article.
For the study, samples of the yellowtail snapper were taken from three areas off the coast of Honduras.
“For every fish, researchers measured the distance between various anatomical landmarks – making 21 measurements in all – and compared these to the overall length of the fish. Because a fish's shape is influenced by the conditions in which it lives, such as ocean depth, currents and diet, this method detected subtle differences in body shape between yellowtail snapper caught at each of the three locations. The team was able to use the method to correctly identify the origins of about 80 percent of the fish in their test sample,” Science Direct said.
The scientists further evaluated the overall effectiveness of simply measuring a fish's shape against other more sophisticated techniques. They did DNA analysis of 15 genetic markers to determine fish origin and analysis of otoliths, otherwise known as fish ear stones, both of which analyses were “time-consuming, technically demanding, and costly” and in the end proved less accurate, the study reports.
Anyone can be trained to do the shape analysis using calipers to hold the fish, the team noted, and they are now working with fishers in Honduras and Belize to collect further body shape data.
Photo courtesy of Steven Canty/Smithsonian
