PREDATOR CONTROL 



line before use. Meehean (1937) 

 recommended using 10 to 12 gallons 

 of kerosene to an acre of water sur- 

 face. The same result can be ob- 

 tained with 4 or 5 gallons of com- 

 mercial fish oil. The fish oil is 

 sprayed on the surface 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. 



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 hatcheryman is not al- 

 lowed 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, and a low chicken-wire 

 fence close to the edge of the pond, 

 or very steep banks around the 

 pond, will keep them out. Some- 

 times, several wires around the 

 pond will work as well. 



Kingfishers are attracted to 

 posts that overlook the water. Re- 

 moving all posts and dead trees 

 near the ponds should help to dis- 

 courage 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 fish. 

 The water snake has a preference 

 for streams but frequents fish 

 ponds. 



Snakes can be controlled by kill- 

 ing 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 de- 

 prive the snake of much-needed 

 cover. Logs, tree roots, and boul- 

 ders should be removed for the 

 same reason. Ponds that are fenced 

 to keep out herons should be pro- 

 vided 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 communities. 



TURTLES 



Some species of turtles are known 

 to be fish eaters and, consequently, 

 are predators if given access to a 

 minnow pond. As a safeguard, 

 all turtles frequenting a pond of 

 minnows should be considered pre- 

 dators and controlled. Turtles can 

 be captured with baited hooks or 

 turtle traps (fig. 25). 



PREDATORY FISH 



Predatory fish and the adults of 

 cannibalistic minnows must be con- 

 trolled in minnow ponds. As men- 

 tioned before, lake and river water 

 should be filtered to keep preda- 

 tory fish fry from entering a pond. 

 When possible, the minnow pond 

 should be drained dry during the 

 winter to kill any predatory fish 

 that may have escaped notice. 

 Ponds that cannot be drained 



63 



