68°F:
Growth or migration routes of salmonoids and egg de—
velopment of perch and smallmouth bass.
55°F :
Spawning and egg development of salmon and trout
(other than lake trout).
48°F :
Spawning and egg development of lake trout, walleye,
northern pike, sauger, and Atlantic salmon.
These temperature standards are based on observations and studies Show—
ing that sh are governed by upper and lower lethal metabolic limits which
are species—specic and that many metabolic changes occur when temper—
ature is raised or lowered. As temperature is increased, both oxygen con—
sumption and heart rate increase. More oxygen is needed at higher temper—
atures because of a higher metabolic rate and the hemoglobin’s lowered
affinity for oxygen. At the same time, however, the amount of oxygen dis—
solved in the water is decreasing. For example, at 33°F carp can surviVe at
oxygen levels as low as 0.5 mg/l. At 95°F the water must contain 1.5 mg/l if
the carp are to survive. Swimming speed (which is used as a laboratory test of
metabolic rate) increases with increasing temperature. For example, salmon
swim twice as fast at 60°F as they do at 35°. As with other biological phenomena, activity may increase with temperature up
to a certain point and
then begin to decline. The swimming speed of a trout increases until the tem—
perature reaches the range of 49—66°F; the trout then begins to slow down.
However, the swimming speed of the minnows on which the trout depends
for food is not affected in the same way; when the temperature” reaches 70°F,
the trout has slowed down to the point that it can no longer catch the min—
nows [19]. A small temperature
4°—can therefore spell life
or death for the trout, even though the higher temperature in itself would not
be lethal.
Disease resistance is also linked to temperature. Not only does resistance
to disease decrease with increasing temperature, but increases in temperature
also increase the rate of microbial activity. Certain bacteria are particularly
lethal to sh. An example is the myxobacterium Chrondroccus columnas.
This bacterium is relatively innocuous below 60°F ; between 60° and 70°F
,
it
may invade wounds; above 70°F, the bacteria can invade healthy, unda—
maged tissue. This bacterium was thought to be responsible for a large sh
kill of blueback salmon in the Columbia River in 1941. Water temperatures
there were exceptionally high during that summer, and on August 20, the
river temperature reached an all—time high of 74.5 °. Of the 25,000 salmon ex—
_
pected on the migration route, only 949 arrived [20].
Temperature increases may become a barrier to sh migration and, in this
way, seriously effect the reproduction of a species. The effects of dam con—
struction in the Columbia Biver area in the State of Washington has been ex—
tensively studied. One study showed that an increase in temperature to more
'
than 70°F delayed passage of salmon from the Columbia Biver into the
Heat as (: Pollutant
Growth or migration routes of salmonoids and egg de—
velopment of perch and smallmouth bass.
55°F :
Spawning and egg development of salmon and trout
(other than lake trout).
48°F :
Spawning and egg development of lake trout, walleye,
northern pike, sauger, and Atlantic salmon.
These temperature standards are based on observations and studies Show—
ing that sh are governed by upper and lower lethal metabolic limits which
are species—specic and that many metabolic changes occur when temper—
ature is raised or lowered. As temperature is increased, both oxygen con—
sumption and heart rate increase. More oxygen is needed at higher temper—
atures because of a higher metabolic rate and the hemoglobin’s lowered
affinity for oxygen. At the same time, however, the amount of oxygen dis—
solved in the water is decreasing. For example, at 33°F carp can surviVe at
oxygen levels as low as 0.5 mg/l. At 95°F the water must contain 1.5 mg/l if
the carp are to survive. Swimming speed (which is used as a laboratory test of
metabolic rate) increases with increasing temperature. For example, salmon
swim twice as fast at 60°F as they do at 35°. As with other biological phenomena, activity may increase with temperature up
to a certain point and
then begin to decline. The swimming speed of a trout increases until the tem—
perature reaches the range of 49—66°F; the trout then begins to slow down.
However, the swimming speed of the minnows on which the trout depends
for food is not affected in the same way; when the temperature” reaches 70°F,
the trout has slowed down to the point that it can no longer catch the min—
nows [19]. A small temperature
4°—can therefore spell life
or death for the trout, even though the higher temperature in itself would not
be lethal.
Disease resistance is also linked to temperature. Not only does resistance
to disease decrease with increasing temperature, but increases in temperature
also increase the rate of microbial activity. Certain bacteria are particularly
lethal to sh. An example is the myxobacterium Chrondroccus columnas.
This bacterium is relatively innocuous below 60°F ; between 60° and 70°F
,
it
may invade wounds; above 70°F, the bacteria can invade healthy, unda—
maged tissue. This bacterium was thought to be responsible for a large sh
kill of blueback salmon in the Columbia River in 1941. Water temperatures
there were exceptionally high during that summer, and on August 20, the
river temperature reached an all—time high of 74.5 °. Of the 25,000 salmon ex—
_
pected on the migration route, only 949 arrived [20].
Temperature increases may become a barrier to sh migration and, in this
way, seriously effect the reproduction of a species. The effects of dam con—
struction in the Columbia Biver area in the State of Washington has been ex—
tensively studied. One study showed that an increase in temperature to more
'
than 70°F delayed passage of salmon from the Columbia Biver into the
Heat as (: Pollutant