11/29/10

In the news: Lake invaders may be killing birds

From the Chicago Tribune:
The hunt is on in the upper reaches of Lake Michigan to count what's believed to be thousands of bird carcasses that have washed ashore this fall — a staggering toll blamed on the disruptive powers of invasive species that have taken root in the Great Lakes.

The great debate in the Asian carp crisis, still playing out in federal court and the halls of Congress, is whether the feared fish has the capability of establishing a thriving population in the Great Lakes. If so, bighead and silver carp will almost certainly, and dramatically, alter commercial and recreational fishing in the nation's largest freshwater body.

But what if, as some scientists suggest, the Great Lakes' natural defenses — plankton shortages, lower water temperatures, greater water depth and swift-moving currents — keep Asian carp from sustaining themselves in large numbers? Will the threat have been avoided?

The answer is that all invasive species bring consequences that few can predict, leading scientists to ponder the thousands of gulls, loons, mergansers and other migratory birds whose remains wash ashore along the white-sand beaches in northern Wisconsin and Michigan's upper peninsula each fall.

There is a somewhat controversial theory for this annual die-off, which by some estimates has claimed more than 100,000 birds in the last 15 years, and it involves a type of naturally occurring but deadly botulism linked to the spread of invasive zebra and quagga mussels, which entered the Great Lakes decades ago aboard ocean vessels. Read more.

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