HATCHERY REQUIREMENTS 



15 



Table 2. suggested chemical values for hatchery water supplies, concen- 

 tration ARE IN PARTS PER MILLION (PPM). (SOURCE: HOWARD N. LARSEN, UNPUB- 

 LISHED.) 



ponds. It also restricts light penetration, thereby limiting photosynthesis 

 and the production of desirable plankton in earthen ponds. 



Pesticides 



Many pesticides are extremely toxic to fish in the low parts- per- billion 

 range. Acute toxicity values for many commonly used insecticides range 

 from 5 to 100 microgram/liter. Much lower concentrations may be toxic 

 upon extended exposure. Even if adult fish are not killed outright, long- 

 term damage to fish populations may occur in environments contaminated 

 with pesticides. The abundance of food organisms may decrease, fry and 

 eggs may die, and growth rates of fish may decline. Pesticides sprayed onto 

 fields may drift over considerable areas, and reach ponds and streams. If 

 watersheds receive heavy applications of pesticides, ponds usually are not 

 suitable for fish production. 



Suggested water quality criteria for salmonid and warmwater fishes are 

 presented in Tables 1 and 2. 



