BROODSTOCK, SPAWNING, AND EGG HANDLING 



191 



Table 21. daily temperature unit REquiRED for egg development of 

 Pacific salmon. 



DAILY TEMPERATURE UNITS 



SPECIES 



TO EYE 



TO HATCH 



TO EMERGE 



Chinook salmon 

 Coho salmon 

 Chum salmon 

 Pink salmon 

 Sockeye salmon 



450 

 450 

 750 

 750 

 900 



750 

 750 



1,100 

 900 



1,200 



1,600 

 1,750 

 1,450 

 1,450 

 1,800 



TEMPERA ri' RE 



Chinook salmon eggs have been incubated at temperatures as high as 6\°F 

 without significant loss. When incubated at 4()°F and below, they have a 

 much higher mortality than those incubated at temperatures of 57 to (iO°F. 

 However, if chinook salmon eggs are allowed to develop to the 128-cell 

 stage in 42°F water, they can tolerate 35°F water for the remainder of the 

 incubation period. Lower temperatures have been experienced by sockeye 

 and chinook in natural spawning environments with fluctuating tempera- 

 tures without adverse affects. The lower threshold temperature for normal 

 development of sockeye salmon is between 40 and 42°F, with an upper 

 threshold temperature between 55 and 57°F. Water temperature appears to 

 be a primary factor in causing yolk-sac constriction in landlocked Atlantic 

 salmon fry. It apparently is triggered by both constant temperature or an 

 excessively warm temperature. Fry raised in cold water with fluctuating 

 temperature do not develop the constriction unless they are moved into a 

 warmer constant temperature. 



Table 22. required daily temperature units for initial development of 



VARIOUS COOL- and WARMWATER SPECIES. 



