The DNA passed on from mother to offspring has provided scientists with a way to track down where sharks were born, and could help in the fight against the shark fin trade.
Conservationists examining the shark fin trade have always had a problem tracking down the origins of fins. Prior to this study the fact that sharks migrate large distances and can also be transported thousands of miles once caught has made tracing shark fins almost impossible.
Now, an international team of scientists lead by the Institute for Ocean Conservation Science at Stony Brook University has an answer.
They used DNA from nearly 400 sharks to establish that groups of Dusky sharks (Carcharhinus obscurus) and Copper sharks (Carcharhinus brachyurus) living in different areas across the globe faithfully give birth in the same area they were born and as such form separate populations of each species.
The genetic information between populations is significantly different meaning that the researchers can essentially use DNA as a ‘post/zip code’ to identify the origin of the fins on sale in Asian markets, enabling better regional monitoring and management of these threatened predators.
The authors are keen to emphasise that while this method could help authorities curb finning it also means that populations of sharks that are overfished are unlikely to recover as there will be no immigration of sharks into the area. This has recently been seen with Dusky sharks in the Western Atlantic whose population is classed as Endangered by IUCN after an 80% decrease in numbers in just 20 years.
Lead Author Martin Benavides said: “Here in the United States, it took only a few decades to nearly wipe out our Dusky sharks, and it will probably take a few centuries for their stocks to be replenished. Our results dash any hopes that dusky sharks from other areas of the world will replenish the depleted U.S. stock.”
Dr. Demian Chapman, leader of the research team added: “We know very little about the shark fin trade, but by using DNA-zip coding we can identify source populations that are contributing most to the trade, and prioritise them for management.”
For further information see: MT Benavides, RL Horn, KA Feldheim, MS Shivji, SC Clarke, S Wintner, L Natanson, M Braccini, JJ Boomer, SJB Gulak, DD Chapman. Global phylogeography of the Dusky shark Carcharhinus obscurus: implications for fisheries management and monitoring the shark fin trade. Endangered Species Research, 2011; 14 (1): 13 DOI.