Tracing the larvae of marine organisms fromwhere they were born to their ultimate destination has been regarded asone of the greatest challenges in ocean science. Managers of marinereserves areas have eagerly sought this information to help determinethe optimal size and spacing of marine reserves; well-planned reservesshould help ensure that protected populations can sustain themselves aswell as provide a source of larvae to maintain exploited populations inareas open to fishing. In a new study, researchers have managed touncover the patterns of local dispersion for a small coral reef fishspecies by employing a combination of inventive tracking techniques. Inaddition to providing ecological information about one particular fishspecies, the work suggests ways that the ecology of other fish can bestudied and applied to strategies for the maintenance of stablepopulations.
Most marine fishes start their lives as tiny larvae, smallerthan a millimeter, and any thought of tagging them to track theirmovements was once considered impossible. However, researchers GeoffJones from James Cook University (Australia), Serge Planes from theUniversity of Perpignan (France), and Simon Thorrold from Woods HoleOceanographic Institute have overcome this problem with a novelapplication of DNA paternity analysis, in combination with a means ofmarking larvae with the antibiotic tetracycline. They show that for thepanda clownfish (Amphiprion polymnus), a significant proportion oflarvae ultimately move less than a few hundred meters away from theirparents. In fact, the researchers found that one third of juvenilessettled within a so-called "natal area" covering just two hectares(less than five acres). Although the other two-thirds of the fish haveyet to be traced, they appear to have travelled in excess of 10 km (6.2mi) away from their birth site. The study also shows that although noindividuals returned to their parents, a few made their home less than50 meters away. (Hence, the authors point out, Nemo the clownfish maynot have been living with his dad, but he might have settled just downthe street.)
Although clownfish spend a relatively short period of time aslarvae (approximately 10 days), the results are significant becausethey document the smallest scale of dispersal known for a marine fishspecies. Clownfish are subject to a thriving aquarium-fish trade inmany tropical countries, and their numbers have been seriouslydepleted. This study provides real hope that marine reserves canprovide the right balance between conserving such species andexploiting them in a sustainable manner.
Geoffrey P. Jones of James Cook University, Australia; Serge Planesof Université de Perpignan, France; and Simon R. Thorrold of Woods HoleOceanographic Institution, Massachusetts. This research was supportedby the Australian Research Council, the National Science Foundation,the TOTAL Foundation, and Populations Fractionnees Et Insulaires.
Jones et al.: "Coral Reef Fish Larvae Settle Close to Home."Publishing in Current Biology, Vol. 15, pages 1314-1318, July 26, 2005.DOI 10.1016/j.cub.2005.06.061 www.current-biology.com
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