8 AQUATIC PLANTS IN POND CULTURE. 



ing away or at least reducing all gross vegetation. This process is 

 laborious and expensive ; the cost of operating a pond-culture station 

 is in fact largely the cost of this periodic clearance of the ponds, and 

 varies with the characteristics of the predominating species of plants. 

 Methods in practice at several stations will be described in a later 

 joortion of this paper. 



Particular kinds of vegetation may of course be also objectionable 

 in specific ways other than with reference to the difficulties of 

 removal at seining time. Large-leaved plants may offer too much 

 shade to j^ermit other plants and the requisite animal life to thrive ; 

 plants of persistent growth may take possession of the ponds and 

 crowd out species more desirable; or plants not in themselves ob- 

 jectionable may not be desired because other obtainable plants are 

 more desirable for the same qualities. The question becomes one of 

 control. Wherever there is soil bottom, vegetation is voluntary, 

 springing up immediately even in artificial ponds, and any attempt 

 to prevent the entrance b}^ natural agencies of water plants common 

 to a region is fraught with much the same difficulties that are en- 

 countered in the attempted exclusion of weeds from a garden. It 

 remains to secure the balance which will bring the conditions nearest 

 to the ideal. 



AQUATIC PLANTS AT THE POND CULTURE STATIONS OF THE 

 BUREAU OF FISHERIES. 



The government work in pond culture, with its wide geographic 

 range, naturally embraces a variety of conditions and affords inter- 

 esting and jDrofitable comparisons. The climate, the quality and 

 temperature of the water, the character of the soil, as well as other 

 factors, make the management of each pond-culture station a sepa- 

 rate problem. The inevitable dependence upon a natural food sup- 

 l^ly for the young fish, hoAvever, concentrates the efforts in such work 

 about the great factor of vegetation, and makes the selection and con- 

 trol of aquatic plants in ponds the most important question, after 

 water supply, that the pond culturist has to contend with. The popu- 

 larity of the basses, crappies, and sunfishes, moreover, and the feasi- 

 bility of increasing their numbers by cultivation, make pond culture 

 a subject of especial interest to people everywhere in the United 

 States, and the Bureau of Fisheries is constantly receiving inquiries 

 and requests for information. The following notes are therefore 

 thought to have interest and value, not only to the professional fish 

 culturist, but to the public generally. They represent efforts to col- 

 lect specimens of all the aquatic plants found at the various pond- 

 culture stations of the Bureau, with observations of the respective 

 superintendents as to the particular value of the desirable species and 



