ESTABLISHING THE HATCHERY 



oxygen and liigher ammonia concen- 

 trations than others and are, there- 

 fore, more successful in fertile 

 ponds. Each species has its limits 

 of tolerance that cannot be exceeded 

 if the production of a pond is to be 

 profitable. 



The productivity of a pond is also 

 related to the hardness of the water. 

 Medium-hard to very-hard water 

 will usually produce more fish than 

 soft water. Sometimes it is possible 

 to increase the hardness of the water 

 by the addition of lime, but fish pro- 

 duction will not increase unless the 

 water contains sufficient nutrients, 

 or a sufficient amount of these ele- 

 ments is added with the lime. 



Seining conditions in natural 

 ponds must be considered before the 

 pond is selected. While it is pos- 

 sible to trap minnows, they often 

 do not move into the traps when 

 needed, and seines must be used to 

 get them out in time for the market. 

 A pond with boggy shores, steep 



banks, soft bottoms, or brushy edges 

 should be avoided unless it has an 

 open, firm-bottomed beach for good 

 seine landings. 



Fertile ponds covered with ice 

 and snow will often run out of oxy- 

 gen before spring, and the fish will 

 smother unless the pond is at least 

 15 feet deep. During winters of no 

 snow, the ice will transmit enough 

 light to keep the plants in the pond 

 actively supplying oxygen and the 

 fish may survive in quite shallow- 

 ponds. During winters of early 

 and heavy snow-s, fish will survive 

 if the ice is kept clear of snow. Be- 

 cause of the difficulties encountered 

 in holding minnows over winter in 

 natural ponds, most dealers plan 

 their production so that all minnows 

 can be sold the first year. When 

 this is not possible, holding ponds 

 with running water are used and the 

 fish are fed artificially through the 

 winter. 



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