Temperature Perception and Responses 227 



The relationship ]:)etween acchmation temperatures and letlial tempera- 

 tures in fishes is undoubtedly a faetor in the survival of fishes transported 

 overland in tanks, particularly where fish are cooled abnormally through 

 the use of ice or refrigerated tanks. 



Table 8.1 Lethal temperatures for three warm-water fishes. 



Largemouth Bass 



Bluegill 



Yellow Perch 



High Temperatures 



Low Temperatures 



Ace. Temp. Lethal Temp. 



20°C(68°F)-32.5°C(90.5"F) 

 25°C(77°F)-34.5°C(94.1°F) 

 30°C(86°F)-36.4°C(97.5°F) 



Ace. Temp. Lethal Temp. 



15°C(59°F)-30.7°C(87.3°F) 

 20°C(68°F)-3L5°C(88.7°F) 

 30°C(86°F)-33.8°C(92.8°F) 



Ace. Temp. Lethal Temp. 



5°C(41°F)-21.3°C(70.3°F) 

 10°C(50°F)-25°C(77°F) 

 15°C(59°F)-27.7°C(81.9°F) 

 25°C(77°F)-29.7°C(85.5°F) 



Ace. Temp. Lethal Temp. 

 20°C(68°F)-5.5°C(41.9°F) 



30"C(86°F)-1L8°C(53.2°F) 



Ace. Temp. Lethal Temp. 



15°C(59°F)-2.5°C(36.5°F) 

 20°C(68°F)-5°C(41°F) 

 25°C(77°F)-7.5°C(45.5°F) 

 30°C(86°F)-11.1°C(51.9°F) 



Ace. Temp. Lethal Temp. 



10°C(50°F)-L1°C(34°F) 



25°C(77°F)-3.7°C(38.7°F) 



Preferred Temperatures 



Anglers have shown considerable interest in the preferred temperatures 

 of sport fishes of various species during summer months because they 

 believe this knowledge will help in locating these fishes, which, of course, 

 is the first step in catching them. Ferguson ^^ made laboratory studies 

 of the preferred temperature of yellow perch and compared his results 

 with preferred temperatures for perch and other species as recorded 

 by other fishery biologists. He used the definition of preferred temperature 

 of Fry^^: "the region, in an infinite range of temperature, at which a 

 given population will congregate with more or less precision— a tempera- 

 ture around which all individuals will ultimately congregate, regardless 

 of their thermal experience before being placed in the gradient." 



The level of thermal acclimation influences the preferred temperature. 

 In general, the preferred temperature is considerably higher than the 

 acclimation temperature for fish that are acclimated to low temperatures. 

 The differences decrease up to the final preferendum where both coincide. 

 In nature a fish may be prevented from selecting its true preferred 

 temperature by light, feeding routines, social behavior and dissolved gases. 



Table 8.2 shows the preferred temperatures of some sport fish. This 

 table represents a part of a table given by Ferguson.^^ Preferred tempera- 



