OPERATING THE HATCHERY 



pickerel weed, will invade the pond 

 rather slowly, and can be controlled 

 by hand or by the use of chemicals. 



Water quality and temperature 

 are controllin*; factors in the effec- 

 tiveness of treatments to kill vege- 

 tation and in the toxicity of the 

 chemicals to fish. Each hatchery 

 presents a different situation with 

 a new set of conditions, so that it 

 is necessary at first to experiment 

 on a small scale with control meas- 

 ures, and modify them to fit the 

 local situation. We can only give 

 general recommendations, which 

 must be adjusted to meet the specific 

 conditions in an area. 



Many things can be done in pond 

 management that will make the con- 

 trol of pond and emergent vegeta- 

 tion simpler. Among these are the 

 following : 



1. A bloom heavy enough to shade out 

 the rooted plants should be maintained 

 throughout the season. A bloom that 

 hides the pond bottom at a depth of 1 

 foot is heavy enough for this purpose. 

 The pond will have to be watched closely, 

 as there is danger that the bloom may 

 become heavy enough to cause an oxygen 

 depletion during warm nights. This 

 method has the advantage of producing 

 fish food while controlling the weeds. 



2. Deep shorelines (at least 18 to 24 

 Inches) at the edge of the bank combined 



with a waterbloom will discourage 

 emergent vegetation, as bulrush, arrow- 

 head, and cattails. 



.'{. Pond banks that can be mowed, 

 with a good cover of hardy grasses, wall 

 discourage invader plants from the shore, 

 such as wildmillet and parrotfeather. 



4. If a bloom is kept on the pond, the 

 repeated cutting of emergents below the 

 surface is an effective means of control- 

 ling undesirable vegetation in the pond. 

 In shallow ponds a scythe will be the 

 most satisfactory tool, but in deep ponds 

 one of the mechanical weed cutters is 

 necessary. When iwssihle, the vegeta- 

 tion should be raked up on the banks to 

 prevent an oxygen depletion when it 

 decomposes. 



CHEMICAL AGENTS 



Subject to local conditions, the 

 following table lists chemical agents 

 which may be used to control the 

 various weed plants. Plants should 

 be treated while they are young and 

 actively growing. Do not wait un- 

 til they become a nuisance, because 

 controls then may be only partly 

 effective and a great deal of time 

 and money will be lost. Always 

 kill the vegetation before the seed 

 forms. The data in the three fol- 

 lowing tables are taken from the 

 Fish-cultural Manual, Region 2, 

 o^lbuquerque, N. Mex., U. S. Fish 

 and Wildlife Service. 



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