98 American Fisheries Society 



Seining the whole pond does so much harm to the plants that 

 it will probably be well to draw the pond in summer and remove 

 both young and old fish, where this can be arranged. In practice 

 it seems to me still better to protect the plants and use all the 

 ponds the whole season, with the idea that the first and last 

 essential of pond culture is food production. But it is not quite 

 enough to protect volunteer plants, nor even to introduce plants 

 at every opportunity. A selection should be made. Some are 

 useful in protecting banks, where these are made of earth. Saw- 

 grass, mint, flags, rushes, sagittaria, pontedaria, water-plantain, 

 water-willow, water-purslane, etc., will do this, but not all are 

 desirable. 



Good qualities may be more than balanced by bad ones, as in 

 the case of cattail flag, which will bind the bottom along the shore 

 line very effectually and provide shade and shelter, but promptly 

 becomes a nuisance by over-crowding and choking out everything 

 else. 



While along the margin a leading purpose of plants may be to 

 protect the banks as well as provide shelter, for the body of the 

 pond the object will be to furnish suitable conditions and pasture 

 for the small creatures necessary for natural fish food. Here is 

 where we all need more light. We do not certainly know just 

 what the various kinds of fish need for food. Nor has it yet been 

 made clear what conditions are most favorable for the production 

 of any kind of food creatures. Our honored ex-president in 

 attacking the problem of how how many food fishes it is possible 

 for the Great Lakes to support included a study of aquatic plants 

 and their dependence on the bottom for the elements of growth. 

 Dr. Raymond H. Pond, as a result of his experiments, states that 

 "the amount of plankton produced by bodies of fresh water is, 

 other things being equal, in some inverse ratio proportional to 

 the amount of its non-rooted vegetation and in some direct ratio 

 proportional to the amount of its gross rooted vegetation." He 

 goes on to draw the inference that: "In the stocking of ponds for 

 fish culture, care should be taken to have a good soil for the 

 bottom; not a stiff clay or sand, but a good loamy soil, such as is 

 favorable for land plants. The species allowed to grow should be 

 those which are known to possess roots and to be very dependent 

 upon the soil, such as Vallisneria spiralis, the so-called fresh 



