January 25th, 2010 by Dave Dempsey
U.S. Fish and Wildlife Service biologists with a bighead carp, one of two species whose entry into the Great Lakes is sparking widespread concern.
Last week’s edition of Great Lakes Asian carp news brought both a U.S. Supreme Court decision and disclosure of the species’ environmental DNA in Lake Michigan. But as members of Congress, state officials and Great Lakes advocates scramble to prevent a self-sustaining Asian carp population in the Great Lakes, a Minnesota commentator has challenged the prevailing wisdom, asking whether such a population would really be so detrimental to the Lakes and their resources. Among other things, commentator Greg Breining argues whether the idea of a “healthy ecosystem” is valid and whether so-called invasive species are often a bad thing.
The suddenly urgent effort to stop the Asian carp entry into the Great Lakes is based on fears that the huge non-native fish might dramatically disturb the $4.5 billion-per-year sportfishery of the Lakes and cause other unforeseen impacts. Growing to 80 pounds or more and consuming up to 40% of their body weight daily, the silver and bighead carp have been likened to “aquatic vacuum cleaners.”
The invasive carp have been traveling northward through the Mississippi River ecosystem since escaping fish farms in the lower part of the watershed, where they were intentionally introduced to control aquatic weed growth. But the discovery late last year of Asian carp DNA close to Lake Michigan, on the wrong side of an electric barrier designed to keep the carp out, has spurred emergency poisoning of fish in the Chicago Sanitary and Ship canal, a lawsuit filed by the State of Michigan to close the canal and locks (the Supreme Court refused to issue an emergency order to do so on January 19), and even an “Asian carp summit” in Washington, D.C.
Meanwhile, the Minnesota commentary challenges the assumptions behind concerns about non-native species, citing academics who question the idea of healthy ecosystems. “When someone is referring to a healthy ecosystem, what they are referring to is an ecosystem the way they want it to be,” says Dr. Mark Davis, chairman of Macalester Colleges’s biology department, in the piece.
“Like it or not, the world is increasingly made up of what scientists have called ‘novel ecosystems’ — biological stews of old and new,” writes Breining.
The commentary also says the non-native zebra mussels in the Great Lakes may be beneficial because they “encapsulate algae,” but research has shown they actually make more nutrients available and may be leading to renewed algae blooms in the lower Great Lakes.
Photo credit: U.S. Fish and Wildlife Service.
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