BROODSTOCK, SPAWNING, AND EGG HANDLING 135 



VARIOUS SPECIES OF FISH AS REPORTED IN THE LITERATURE. TEMPERATURE 



REMARKS 



Upstream migration and maturation, 4.')-()() , eggs that had developed to the 128-cell stage in 

 42.5° water could tolerate water at 3.")° for the remainder of the incubation period. The 128- 

 cell stage was attained in 144 hours of incubation. 



Eggs reached the 128-cell stage in 72 hours at 42. .5° but required an additional 24 hours of 

 development at that temperature before they could withstand 35° water. 



Temperatures in excess of 54° affect maturation of eggs and sperm in adults; normal growth 

 and development of eggs does not proceed at temperatures above 49°; at least 50" mortality 

 at 54° can be expected. 



Broodfish should not be held in water temperatures exceeding 56°, and preferably not above 

 54° for at least six months before spawning. Rainbow trout eggs will not develop normally in 

 the broodfish if constant water temperatures above 56° are encountered prior to spawning. 

 The eggs cannot be incubated in water below 42° without excessive loss. 



Broodfish can tolerate temperatures greater than 66° but the average water temperature should 

 be 48-50° for optimal spawning activity and embryo survival. Eggs will develop normally at 

 the lower temperatures, but mortalities are likely to be high. 



Eggs do exceptionally well in hard water at 50° 



Water temperatures should not drop during the spawning season. Temperatures near an 

 optimum of 54° are recommended in northern pike management. 



The optimum temperature ranges for fertilization, incubation, and fry survival are 43-54°, 

 48-59°, 59-70°, respectively. If unusually cold weather occurs after the fry hatch, fry survival 

 may be affected. Feeding of fry may also be reduced when temperatures are low. 



Temperature shock between 65° and higher temperatures may have a more deleterious affect 

 on freshly fertilized eggs than if the eggs are incubated for 16 to 44- hours at 65° before 

 transfer to the higher water temperatures. 



