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Dead alewives on a Lake Michigan beach.
-
Lake Michigan's ecosystem was upset by the introduction of two ocean fish, the
lamprey and the alewite, when the St. Lawrence Seaway opened a channel between the Atlantic Ocean and the Great Lakes. The lampreys decimated the lake
trout. The alewife population, at first controlled by the trout, increased beyond
proper proportions. Not well adapted to freshwater conditions, the alewives were
vulnerable to the lake's comparatively rapid temperature changes. In the summer of
1967, dead alewives piled up on the beaches of the lake,— their decaying carcasses
added phosphates to the lake water, intensitying eutrophication.— Subsequently,
coho salmon, introduced to replace the trout for sport and commercial fishing and to
control the alewives, became contaminated with DBT.
4
Assault on a Lake
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€
a.
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'
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&.
,
.
-
v,
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-f
,
c
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Dead alewives on a Lake Michigan beach.
-
Lake Michigan's ecosystem was upset by the introduction of two ocean fish, the
lamprey and the alewite, when the St. Lawrence Seaway opened a channel between the Atlantic Ocean and the Great Lakes. The lampreys decimated the lake
trout. The alewife population, at first controlled by the trout, increased beyond
proper proportions. Not well adapted to freshwater conditions, the alewives were
vulnerable to the lake's comparatively rapid temperature changes. In the summer of
1967, dead alewives piled up on the beaches of the lake,— their decaying carcasses
added phosphates to the lake water, intensitying eutrophication.— Subsequently,
coho salmon, introduced to replace the trout for sport and commercial fishing and to
control the alewives, became contaminated with DBT.
4
Assault on a Lake