t)8 U. S. BUREAU OF FISHERIES. 



2 inches thick, 1 foot wide, and 4 feet lontr is inserted in the grooves 

 in the ends of the tlivision wall to retain tlie fish, while the remaining 

 portion of the pond is being cleaned. The dam board has a saw 

 tooth edge permitting the overflow water to pass but preventing 

 the escape of the fish. 



The " push screen " consists of a frame made of 1 by 4 inch lum- 

 ber, to which is attached poultry netting of 1-inch mesh or smaller 

 if the size of the fish requires. The smaller dimension of the lumber 

 forms the face of the screen, to offer but slight resistance when being 

 pushed through the water. Its shape conforms to the shape of the 

 ponds. At Manchester the sides flare outward. In size it is some- 

 what shorter than the width of the pond for convenient handling, 

 and to prevent the escape of fish around the ends strips of heavy 

 duck or canvas belting are attached to each end of the screen. Iron 

 staples driven into the bottom board at suitable intervals and slightly 

 protruding will serve to keep the board from dragging on the bot- 

 tom of the pond and facilitate the easy movement of the screen 

 through the pond. 



rOND OUTLET AND " KETFL-E." 



As being of possible interest and value to persons interested in the 

 subject a drawing of the pond outlet and " kettle " previously men- 

 tioned (p. G4), with descriptive text and specifications for construc- 

 tion, are given (Fig. 3). 



In referring to the cut of the pond outlet and " kettle " it will be 

 noted that it contains features not embodied in other constructions 

 of a similar character. The drain box is made in about the same 

 manner as those now in use at many stations, but in place of the 

 wooden dam boards it has a cement dam B^ the height of which 

 is determined by the water level when tlie pond is filled. If it is 

 desired to raise the water level of the pond, the wooden dam boards 

 can be dropped in the slot ('. The screen I> is the same as those 

 now in use. To draw down the water in the pond, a gate valve A 

 is so placed at the bottom that all of it can be drawn through the 

 kettle. To make this removable, a flanged valve of the standard 

 low-pressure type is used. A short nipple with a flange on one end 

 is placed in the forms when making the drain box. Later a rubber 

 gasket is cut to size and the gate valve is bolted into place. It is 

 not necessary to bolt tlie valve around tlie bottom, since it may be 

 desirable at some time to remove it, and it would l)e a difficult matter 

 to get at bolts so located. A G-inch gate valve as described above 

 measures approximately KH inches from face to face of flanges. 

 Therefore, a standard valve should be used in place of the medium or 

 heavy service valves. It will be necessary to place the flange of the 

 nipple as close to the cement dam B as possible. Therefore, the 

 bolts should be put in place before cementing. 



Another feature of the plan is the construction of a cement 

 "kettle" in front of the drain box. It will be noted that the side 

 walls of this kettle extend approximately 12 inches above the earth 

 floor of the pond, so that in drawing down the water in the pond 

 when it drofjs below this point it must then enter at the sluice gates /. 

 The small fish will be drawn clown through these gates and will 

 immediately seek the more quiet water at the upper end of the kettle. 



