Contaminants reveal tuna’s origins
KEN NEILL
been exposed to these chemical tuna tissue samples) to two chlorBluefin tuna in the Atlantic Ocean compounds, and it further condane compounds (trans-nonare roughly divided into two firms past findings of a fish’s achlor and cis-nonachlor). The populations along either side of starting point. For example, the team found different ratios of the 45° W meridian. Because the nonachlor-to-PCB ratios of fish chlordanes-to-PCBs in fish from relatively recent discovery of this from the western North Atlantic the Mediterranean and western demarcation has implications for are similar to those of fish in the North Atlantic (where the populamanaging stocks of the commerGulf of Mexico feeding grounds; tion is critically endangered). cially lucrative fish, scientists and this indicates that the North fisheries managers want to Atlantic fish ate their way trace the birthplaces and down the U.S. east coast and journeys of the fish. Redid not come from the searchers have used methods Mediterranean. such as satellite-tracking tags Preliminary results from and isotope signals from the the new method show that fishes’ ear bones. Now, a more fish travel from the team publishing in ES&T Mediterranean to the western (2009, DOI 10.1021/ North Atlantic to feed than es901810e) reports a different originally thought. “We found tracer to determine geothat 13% of the eastern fishgraphic origins for bluefin ery traveled west, accounting tuna: pesticides and PCBs. for 70% of juveniles, on averAlong with two other studage, in the western North Aties, the new work was funded by the Large Pelagics This foot-long young-of-the-year bluefin tuna spawned lantic,” says Dickhut. “Because the eastern stock is Research Center at the Uni- in April or May of 2008 in the Gulf of Mexico and 5-10 times larger than the versity of New Hampshire to was caught 50 miles off Virginia in September that year. western stock, movement of examine Atlantic bluefin only a relatively small portion stock structure. “The studies They determined that those ratios of the eastern stock to the west present a consistent and complechanged after about a year if fish has a big influence.” mentary overview of current mixmigrated, because these animals The International Commission ing rates of eastern and western tend to grow and incorporate for the Conservation of Atlantic bluefin tuna,” wrote Molly Lutcontaminants without evacuating Tunas (ICCAT) sets catch limits cavage, director of the center, in them from their bodies. for tuna and related species and an email. The year-old bluefin tuna proreviews emerging science. The The new results confirm previvided a “smoking gun” for the organization initiated a 15-year ous findings from satellite tags team’s method, says coauthor recovery plan for Atlantic bluefin and otolithssfish ear bonesson John Graves, a geneticist at VIMS. tuna in 2007 in hopes of stemhow and where these fish interJuvenile fish from the Mediterraming the fisheries’ collapse. mingle while feeding: past work nean are more likely than adults The European Commission’s has shown that up to nearly twoto travel across the Atlantic, hitfisheries unit noted that the ICCAT thirds of the tuna in the Mid-Atting foraging grounds in the westrecovery plan may be the only lantic Bight could be from the ern North Atlantic. Because the hope for the species’ future: on eastern fishery. The new method pesticide chlordane is banned in September 21, European Commisindicates that 33-83% of juvenile the EU, finding it in fish spawning sion member states blocked a tembluefin tuna captured in the Midin the Mediterranean immediately porary halt to international trade of Atlantic Bight have eastern origins signals that they have made that Atlantic bluefin tuna. If that recomand that mixing within a feeding cross-Atlantic journey, says mendation had passed, the EU ground varies with time and Graves. would have proposed the fish for space. The team proposes that the raendangered status under the ConDeveloped by Rebecca Dickhut tio of compounds in a fish makes vention on International Trade in of the Virginia Institute of Marine the method universal, by removEndangered Species of Wild Fauna Studies (VIMS) and her coling issues of size and age, says and Flora in March 2010. leagues, the method uses ratios of Dickhut. This lets the scientists two PCBs (PCB153 and PCB187, —NAOMI LUBICK figure out how long the fish have both of which are prominent in 10.1021/es903057g
2009 American Chemical Society
Published on Web 10/21/2009
November 15, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 8477
