46 Interrelationships of Fishes and Lake Habitats 



brook trout to high temperatures. Fry ^^ states that 77.5°F is the lethal 

 temperature for brook trout upon prolonged exposure. During the summer 

 of 1951, surface temperatures of a pond fed by a small amount of spring 

 seepage remained between 75° and 79°F for 24 days, and no loss of 

 trout occurred. At the same time, the maximum bottom temperature was 

 74°F. 



Typical warm-water fish are the largemouth bass, bluegill, black and 

 white crappie, and yellow bullhead. These fishes, in ponds and lakes, are 

 almost never killed by high temperatures alone. Intermediate between 

 the trouts and the fishes listed above are such species as the smallmouth 

 bass, rock bass, walleye, northern pike, and the muskellunge. There is 

 no question but that these are somewhat more sensitive to high water 

 temperatures than are more typical warm-water species; however, there 

 is some evidence to indicate that factors other than temperature limit 

 their distribution in certain types of warm- water habitats. While tem- 

 perature in itself may not be a limiting factor for most species, high ones 

 are usually associated with other conditions which culminate in an un- 

 satisfactory habitat. 



Water temperatures influence rate of metabolism and therefore the 

 growth rate; they are often critical in their relationship to spawning and 

 the development of normal embryos. A general knowledge of temperature 

 requirements of common fishes is of value to a fishery biologist because 

 with it he may be able to prevent the release of fish stocks in thermally 

 unsuitable waters. 



More will be said of the physiological effects of temperature change on 

 fishes in Chapter 8. 



EFFECTS OF TURBIDITY 



When rain falling upon the lands runs off into watercourses, it carries 

 a greater or lesser amount of soil with it in the form of silt particles. In 

 certain parts of the United States, these particles are so finely divided that, 

 once they become suspended by water, they fail to settle. This is because 

 the very fine particles carry an electrical charge and, therefore, tend to 

 repel one another whenever they come close together. Since Oklahoma 

 contains extensive areas where these colloidal soil particles are present, 

 the problem of pond and lake turbidity is of considerable importance 

 within that state. Irwin,^" writing of ponds in Oklahoma, states that in 

 the clay-soil region, ponds had clear water for at least the first year if 

 their basins were covered with vegetation at the time of impoundment. 

 However, excavated ponds from which the vegetation had been removed 

 had muddy water from the first. Also, older ponds, that had been drained, 

 had had the silt removed, and then were refilled, usually had muddy 



