Contact: Jim Erickson, (734) 647-1842, email@example.com
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,
hatched round gobies leave their lake-bottom homes and swim to the
nocturnal migration – never before documented among round gobies --
boosts the chances
that large numbers of hatchlings will get sucked into the ballast tanks
Jude and Hensler report their findings in the
of the Journal of Great Lakes Research. In addition to uncovering a
unknown chapter in the life history of the round goby, the authors say
results have implications for ballast-water management on freighters
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
only take on ballast water at the surface and only during the day, it
reduce the likelihood of introducing new species and spreading existing
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
system, in1990 on the St. Clair River northeast of
Jude and Hensler launched the latest study several
after unexpectedly finding newly hatched round gobies in surface nets
towed at night
Follow-up efforts included a trip to western
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
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