234 



BUI.I.ETIN OI^ THE BUREAU OI^ I^ISHERIES. 



weeds, with close-cut turf extending to the water's edge, may add to the sightliness of the 

 pond, but it will operate against the odonate fauna. The larger vegetation is not neces- 

 sary; an area covered with tall weeds and grass somewhere around the margin of the 

 pond will prove amply sufficient. 



If the breeding of fish and the rearing of forage for their consumption is confined 

 to a single pond, of course that will be the place to stock with odonate eggs or nymphs. 

 With proper care such combined breeding may be carried on successfully in the same 

 pond, as is done at Fairport. "If not overstocked, the average pond may be managed 

 so that it will furnish all the live food necessary for the adult fish," (Johnson and Staple- 

 ton, 1915, p. 19.) 



In the last few years the forage problem in connection with fish culture has been 

 receiving much more attention here in the United States. Embody (191 5, p. 233) noted 

 that *'The propagation of minute organisms in great numbers as food for young fishes 

 has been accomplished by the Chinese and the Japanese and more recently by the 

 Germans," and he recommeded small forage ponds in connection with the larger fish 

 pond (p. 235) : 



There is good reason for believing that the supply of aquatic insects can be materially increased 

 by building a few small breeding ponds along the margin of the main pond and excluding all fishes there- 

 from. Certain insects will naturally deposit their eggs in both breeding and main ponds. There are no 

 very destructive insects in the former; hence there are sure to emerge a goodly number of adults, which, 

 in turn, will continue year after year to repopulate the small ponds, as well as the main pond. 



Needham and Lloyd have advocated the same idea in The Life of Inland Waters 

 (191 6). In figure 242, on page 408, they present a diagram illustrating conditions 

 advisable for intensive fish raising on an 8o-acre tract of wet upland traversed by a trout 

 stream. The noticeable thing about it is the large area, 40 acres of ponds, to be placed 

 under control for the production of fish forage. 



Until experiments have been tried out in a practical way for some length of time, 

 it will be impossible to decide definitely how much breeding area is necessary or advisable 

 in order to produce the amount of food forage requisite for a given number of fish. 

 Meanwhile, if forage breeding is to be attempted, the place to put the odonate eggs and 

 nymphs will be with the other fish food in the breeding ponds, as well as in the main 

 fishpond. Once well started in both places they will thereafter propagate themselves, as 

 Embody has stated. 



Securing the Stock Materiai,. — The method of securing the necessary odonate 

 eggs or nymphs for stocking the pond will vary with the time of year. If the fishpond 

 is to be started in the spring or fall, the best odonate material to put in it will be the 

 nymphs. These may be collected from the nearest pond or from the still water of a stream 

 or river. Some nymphs inhabit running water or places where there is a perceptible 

 current, but such species are not suited for pond life. 



An old ditch well choked with algae and water plants, and in which the water stands 

 throughout the year, is an admirable source whence to obtain the nymphs. There are two 

 good methods of collecting them, and it would be well to use both. If there is much 

 loose algae and debris over the bottom of the ditch, the best implement to use is the com- 

 mon garden rake, as advised by Needham (1899). The collector can stand on the shore 

 and rake the algae and weeds out of the water onto the ground in front of him. As the 

 water drains off the nymphs will make active efforts to get back, and are thus easily 

 found and secured. 



