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Becker, George C. / Fishes of Wisconsin
(1983)

Wisconsin waters,   pp. 3-17 PDF (5.6 MB)


Page 14

 
14    Wisconsin Waters 
  Edsall calculated the expected growth of the electricity-generating industry
on Lake Michigan from 1968 to 2000 and estimated daily water consumption
and the percentage of littoral zone waters that would be used (1976:456):
                              Flow Percentage of Littoral Zone 
                       Year   (cms)  Waters Used per Day 
                       1968     188        0.082 
                       2000   2,582        1.124 
The above estimates were developed under the assumptions that stations would
operate at 100% capacity and that the temperature of the cooling water would
rise by 11°C (20'F). The littoral zone waters occupy the shoreline to
the 9-meter 
depth contour. 
   Edsall (1976) and Tait (1973) noted that the littoral waters are used
by almost 
all the fish in a large lake. The warmwater fishes of the Great Lakes are
essen- 
tially permanent residents of the littoral waters. Species such as the lake
trout 
and most whitefishes, generally inhabitants of the cold waters farther off
shore, 
use the littoral waters during the cool portions of the year as feeding and
spawn- 
ing grounds, and also as nursery areas for their young. Several species of
trout 
and salmon, and various other species which ascend tributary streams to spawn,
must pass through the littoral waters on their way to and from the spawning
grounds; and their offspring must pass through these waters when they migrate
from the spawning streams to the open waters of the Great Lakes, where they
grow to maturity and harvestable size. Studies clearly show that large numbers
of fish are killed by impingement on intake screens of power plants and that
fish eggs and fry are being entrained at power plants, with resulting high
mor- 
tality. 
   During the years 1975-1976, an estimated 2,754,118 fish weighing a total
of 
49,630 kg were sucked into the cooling water intake of the Oak Creek power
plant (Milwaukee County) (P. Hayes, The Milwaukee Journal 17 October 1976).
Scientists estimated that more than 90% of these were alewives and smelt,
but 
635 trout and 190 salmon were also counted. At four power plants-Point Beach
north of Manitowoc, Port Washington, Lakeside at St. Francis, and Oak Creek-
almost 6 million fish weighing 149,053 kg were caught on the intake screens.
Of 
these, 6,863 were trout or salmon weighing a total of 4,191 kg. At the same
time, 
millions of newly hatched fish, fish eggs, and plankton were being sucked
through 
the screens into the plant and then ejected, often with killing effect. 
   Investigators have noted that high concentrations of predator fish may
gather 
in the plume from a thermal outfall; the fish are attracted by the abundance
of 
food organisms (including other fish) which have passed through the cooling
system, and which may be damaged or dead. Reports of mortalities caused by
heat shock, cold shock, air embolisms, and chlorine treatment of cooling
water 
are available in the literature. 
   According to Tait (1973), pesticides and heavy metals accumulate in the
bod- 
ies of fishes much more rapidly in water of high temperatures. It has also
been 
shown that some disease outbreaks in fish are much more severe at high envi-
ronmental temperatures, and the concentration of fish in thermal plumes may
facilitate the passage of disease organisms from one fish to another. 


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