WEED CONTROL 



dispensable to the hatchery opera- 

 tor who wishes to produce a year- 

 round bait supply from his produc- 

 tion ponds. Minnows for the early 

 fishing season must be over-win- 

 tered in ponds that will maintain an 

 ample supply of oxygen through the 

 longest winter. 



The most satisfactory ponds are 

 those supplied with an ample 

 amount of oxygen-bearing, running 

 water from rivers, creeks, springs, 

 or flowing wells. There are advan- 

 tages and disadvantages to all of 

 these sources. Water from unpol- 

 luted rivers and creeks is usually 

 high in oxygen and contains some 

 natural minnow foods, but it may 

 not always be of the right tem- 

 perature. Water from springs and 

 flowing wells is usually cool and of 

 uniform temperature, but it is often 

 low in oxygen and is always low 

 in natural minnow foods. Spring- 

 w^ater must usually be run over a 

 riffle before it enters the pond. This 

 means that fish held in ponds sup- 

 plied with stream water will not 

 need as much artificial food, but 

 they must be moved to growing 

 ponds before the water warms up 

 in the summer. Minnows held in 

 spring-water ponds can be left in 

 the j)onds all year round, but they 

 will require large amounts of artifi- 

 cial food. 



Holding ponds should be small 

 enough and shallow enough so that 

 the fish can be readily removed 

 whenever they are needed. An acre 

 pond that is 4 or 5 feet deep is very 

 practical, and a number of small 

 ponds is preferable to one large 



pond because different species and 

 different sizes of minnows can be 

 held separately in the small ponds. 

 This usually reduces losses and 

 minimizes the sorting operations in 

 the spring. 



In areas where holding-pond con- 

 struction is not practical, minnows 

 can be overwintered in production 

 ponds, if the ice is kept free of 

 snow all winter. There are several 

 ways to remove snow from the 

 ponds, but the use of soot spread 

 thinly over the snow seems the most 

 practical. The soot absorbs enough 

 heat from the sun to melt 6 to 9 

 inches of snow and ice. In areas 

 of light snow, plowing may be prac- 

 tical, but in regions of 3- to 6- 

 foot snowfalls plowing is very ex- 

 pensive. Some operators use a 

 centrifugal pump to spray water 

 over the snow ; the resulting slushy 

 condition usually freezes to clear 

 ice that transmits enough light to 

 keep the plants producing oxygen. 



WEED CONTROL IN 

 PONDS 



With good pond management, 

 weed control is generally not a prob- 

 lem. Ponds that are farmed inten- 

 sively are heavily fertilized, either 

 directly by the use of fertilizers or 

 indirectly by food that is not picked 

 up by the fish and by the heavy 

 concentration of excretory products 

 that results from large populations. 

 Under these conditions, submerged 

 vegetation will be controlled by the 

 waterbloom produced, and emer- 

 gent vegetation such as cattails or 



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