Environmental Engineering Reference
In-Depth Information
increase in temperature from 13 to 23°C is accompanied by a 22% de-
crease in viscosity. General molecular adaptations to temperature extremes
were described in Chapter 15. Physiological characteristics interact to de-
termine the optimal temperature for growth as mediated by energetic con-
straints. For example, even though salmonid species seem very similar, they
have different temperature requirements for growth and survival (Table
21.1). Fish seek water that has a temperature near their optimal growth
temperature.
Temperature requirements for reproduction may be more stringent
than those for survival or growth. Temperature constraints of fishes in
freshwaters and interactions with trophic state have led fisheries managers
to consider lakes to be of several general types of thermal regimes with re-
gard to commercial or sports fishes (Fig. 21.6): (i) warm waters dominated
by black, white, yellow, and striped basses, sunfish, perch, or catfish;
(ii) cool waters with some of the previously mentioned species plus wall-
eye and pike; (iii) cold waters dominated by salmonids; and (iv) two-story
waters in stratified lakes with oxygenated hypolimnia in which cool-water
and cold-water species can find refuge from high water temperatures dur-
ing the summer. During summer months, cold- or cool-water species are
hypolimnetic, and warm-water fishes reside in the epilimnion.
Oxygen is crucial for fish. The problem of fish kills related to O 2 deple-
tion was described in Chapter 11. The O 2 requirement is greater as temper-
ature increases, and the concentration of O 2 that can be dissolved in warmer
water is lower. Fish can respond to lower O 2 by increasing ventilation rate.
Although increased ventilation allows survival under marginal O 2 concentra-
tions, it uses energy and causes stress. Some species of fish can actually use
atmospheric O 2 , but most will die if dissolved O 2 concentration becomes too
low. Temporary anoxia can be withstood by many species, but repeated bouts
of anoxia can lead to cumulative harmful effects (Hughes, 1981).
Food quantity and quality can alter the survival, reproduction, and
growth of fishes. Thus, fishes are selective in what they eat (Hughes, 1997).
All fishes require protein, carbohydrates, lipids, vitamins, and minerals. A
fish that is piscivorous may be able to obtain reasonable amounts of pro-
tein and lipids but be limited by the energy content of its food. Zoo-
planktivorous fishes may have diets that are rich in lipids, and many teleost
fishes have a high lipid requirement. Thus, copepods that contain high con-
Temperature Requirements for Various Salmonid Species a
TABLE 21.1
Maximum
Maximum
Spawning
Species
growth (
C)
temperature (
C)
temperature (
C)
Atlantic salmon (Salmo salar)
13-15
16-17
0-8
Brown trout (Salmo trutta)
12
19
2-10
Rainbow trout (Onchorhynchus mykiss)
14
20-21
4-10
American brook trout (Salvelinus fontinalis)
12-14
19
2-10
Grayling
10-16
20
10
a Note how maximum growth rate occurs at a temperature only slightly less than the maximum for survival,
and the temperature required for reproduction is much less than that for maximum growth (after Templeton,
1995).
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