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Aug.16, 2007 Contact: Jim Erickson, (734) 647-1842, ericksn@umich.edu Round gobies rising: U-M researchers say
nightly swim to surface helped the
invasive fish spread swiftly through
Oceangoing freighters were the prime suspects, right from the start. But round gobies are bottom-dwelling fish, so how could significant numbers of them get inside ships that normally take on ballast water close to the surface? "It's been a mystery to us as to how they were getting on board. We've been scratching our heads about how that happened," said Jude, a research scientist at the U-M School of Natural Resources and Environment. Now Jude and U-M graduate student Stephen Hensler say they've found the answer: synchronized swimming on a grand scale. At night during the summer breeding season,
countless newly
hatched round gobies leave their lake-bottom homes and swim to the
surface. This
nocturnal migration – never before documented among round gobies --
boosts the chances
that large numbers of hatchlings will get sucked into the ballast tanks
of Jude and Hensler report their findings in the
current issue
of the Journal of Great Lakes Research. In addition to uncovering a
previously
unknown chapter in the life history of the round goby, the authors say
their
results have implications for ballast-water management on freighters
that visit
Newborn fish of many other species – as well as tiny aquatic animals called zooplankton -- are known to rise to the surface at night and descend to the depths after sunrise, following food and evading predators, Hensler said. "If you had some sort of policy whereby ships
would
only take on ballast water at the surface and only during the day, it
would
reduce the likelihood of introducing new species and spreading existing
ones
around," said Hensler, a doctoral student at the School of Natural
Resources and Environment. The voracious and aggressive round goby is native to the Caspian and Black seas in eastern Europe. Anglers despise them because they steal bait from hooks. Scientists say round gobies have disrupted the Jude was the first to find round gobies in the
Great Lakes
system, in1990 on the St. Clair River northeast of Jude and Hensler launched the latest study several
years ago
after unexpectedly finding newly hatched round gobies in surface nets
towed at night
on Follow-up efforts included a trip to western In the U-M fish-collection trips to Lake Michigan and The Hensler and Jude research article is available at: http://www.iaglr.org/jglr/db/show_article.php?file_name=2007/num2/33_2_295-302.pdf For more information about David Jude, visit: http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=394 # # # # # # Jim Erickson News Service University of Michigan 412 Maynard Ann Arbor, MI 48109-1399 Direct: 734-647-1842 Main: 734-764-7260 Fax: 734-764-7084 Office web: http://www.umich.edu/news |