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Kitchi-Gami
Almanac
Divers Find Zebra Mussels at Isle Royale
Zebra mussels were discovered for the first time this fall at
Isle Royale National Park in northwest Lake Superior. Divers found the
invasive mussels while doing an assessment of shipwreck sites.
The primary spot is at Windigo, on the west side of the
island in Washington Harbor, according to Superintendent Phyllis Green.
Also, a single mussel was found at Mott Island dock on the east end.
The park is analyzing the threat and will form a team to work on
containing it.
“What’s critical is whether they were actually breeding,”
Phyllis says. “If they were not sexually active, it will make
containment through removal much easier.”
Zebra mussels have been in the Great Lakes since the 1980s,
arriving in ballast tanks of oceangoing ships and clogging critical
intake pipes.
At Isle Royale, besides the danger to native mussels and to
inland lakes, there’s concern that the invasive species could threaten
the park’s shipwrecks.
History Notes
 December 7, 1968: Ironwood, Michigan’s first
snowmobile derby, with 650 entries. Michigan History Magazine
January 1, 1969: Split Rock Lighthouse closes
after 59 years of service. It becomes a state park the following year.
Lighthouse Friends
January 1, 1970: Port Arthur and Fort William
merge to become Thunder Bay, Ontario. Environment Canada
January 25, 1983: Appeals Court rules Ojibway
bands of Lake Superior legally retain hunting, fishing and gathering
rights under treaties of 1837, 1842 and 1854. Wisconsin Historical
Society
Lake Levels
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The levels on the hydrographs are shown in both feet
and
meters above (+) or below (-) Chart Datum. Chart Datum, also known as
Low Water Datum, for Lake Superior is 601.1 feet (183.2 meters). It is
a reference plane to which water depth and Federal navigation
improvement depths on navigation charts are referred.
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