8 FISH HATCHERY MANA(;KMKNT 



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X 



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CO 



Op SMALL FISH SURVIVE SHORT EXPOSURE 



0.3 



1.0 



2.0 



3.0 



4.0 



5.0 



LETHAL IF EXPOSURE PROLONGED 



FISH SURVIVE, BUT GROWTH SLOW 

 FOR PROLONGED EXPOSURE 





DESIRABLE RANGE 



Figure 4. Effects of dissolved oxygen on warm water pond fish. 

 Milligrams/liter = parts per million. (Source: Swingle 1969.) 



concentrations near 4-5 parts per million, and these fish will die if it drops 

 below 3 parts per million. Walleye fry do not survive well in water contain- 

 ing 3 parts per million dissolved oxygen or less. Low levels of dissolved 

 oxygen below 5 parts per million can cause deformities of striped bass dur- 

 ing embryonic development. 



NITROGEN 



Molecular nitrogen (N;) may be fixed by some aquatic bacteria and algae, 

 but it is biologically inert as far as fish are concerned. Dissolved nitrogen 

 may be ignored in fish culture so long as it remains at 100% saturation or 

 below. However, at supersaturation levels as low as 102"^ it can induce gas 

 bubble disease in fish. 



