61 



cod-liver oil must be mixed with gasoline before use. 

 Meehean (1937) recommended using 10 to 12 gallons of 

 kerosene per acre of water-surface. The same result 

 can be obtained with 4 or 5 gallons of commercial fish 

 oil. The fish oil is sprayed on the surface in order 

 to control the thickness of the film. Kerosene becomes 

 too thin to be effective when sprayed, so it is best 

 poured along the windward side of the pond. These oils 

 are not injurious to the fish. 



BIRDS 



Herons and kingfishers may cause a heavy loss of 

 fish from ponds. Occasionally the entire production 

 of a pond has been taken by birds. The private hatch- 

 eryman is not allowed to shoot or trap these birds; so 

 he must depend on scares, wires, and fences to keep 

 them from the ponds. 



Herons do not usually alight in the water; a low 

 chicken-wire fence close to the edge of the pond or 

 very steep banks around the pond will keep the birds 

 out. Sometimes several wires around the pond will 

 work as well. 



Kingfishers are attracted to posts that overlook 

 the pond. Removing all posts and dead trees near the 

 ponds should help to discourage these birds. 



The hatchery operator should try to keep predatory 

 birds from his pond, as the heron spreads the yellow 

 grub and the kingfisher is host to the black grub. 



SNAKES 



A large percentage of the food of the common water 

 snake and some garter snakes consists of fishes. The 

 water snake has a preference -for streams but will 

 readily frequent fish ponds. 



Snakes can be controlled by killing all that are 

 seen around the ponds. The grass and weeds at the edge 

 of the pond should be cut short at all times so as to 

 deprive the snake of much needed cover. Logs, tree 

 roots, and boulders should be removed for the same 

 reason. Ponds that are fenced to keep out herons 

 should be provided with pits at intervals along the 

 outside of the fence to catch snakes and turtles. 

 Water-snake traps are now advertised for sale in some 

 c i ties. 



