HATCHERY REQUIREMENTS 



5 10 15 20 25 30 



Water temperatures "Cent. 



^>o<> 



Oxygen mgm per liter (PPM) 

 5 6 7 8 9 10 11 12 13 H 15 16 17 



i J ij j i| i ,i u l || i, i ii;ii|l | i,i|ii| i |i Jr ii|i| i ; iNlM i |i || lMl | ll l ^ |l M |I ^Ni l »^lM ||| l l|l M |l||||;||| ^| |l||^ | ; l^ l M l M |||l ^ || ^ l |P ||| ^ 



I'l'I 'M ^'i ' l'i' 



5 6 7 



Oxygen cc per liter 



10 



11 



12 



Figure 1. Rawson's nomagram of oxygen saturation values at different tempera- 

 tures and altitudes. Hold ruler or dark-colored thread to join an observed tem- 

 perature on the upper scale with the observed dissolved-oxygen value on the 

 lower scale. The values or units desired are read at points where the thread or 

 ruler crosses the other scale. The associated table supplies correction values for 

 oxygen saturation at various altitudes. For example, if 6.4 ppm of oxygen is 

 observed in a sample having an altitude of approximately 500 m (l,640 feet), the 

 amount of oxygen that would be present at sea level under the same cir- 

 cumstances is found by multiplying 6.4 by the factor 1.06, giving the product 

 6.8; then the percentage saturation is determined by connecting 6.8 on the lower 

 scale with the observed temperature on top scale and noting point of intersection 

 on the middle (diagonal) scale. 



OXYGEN 



Oxygen is the second-most abundant gas in water (nitrogen is the first) 

 and by far the most important — fish cannot live without it. Concentrations 

 of oxygen, like those of other gases, typically are expressed either as parts 

 per million by weight, or as percent of saturation. In the latter case, satura- 

 tion refers to the amount of a gas dissolved when the water and atmos- 

 pheric phases are in equilibrium. This equilibrium amount (for any gas) 



