Part III.] Pond Fish Culture. 167 



The Crayfish. 



It might not seem fair to place crayfish under the head of 

 "Enemies of Fish." In one sense crayfish should be considered 

 as an important element — as a good food for certain kinds of 

 fish. The crayfish is eaten by the bass, the crappie, the sun- 

 fish, and the catfish. They are especially devoured when they 

 are young. The large bass and catfish also feed extensively 

 upon full-grown crayfish when the latter are present. Bass 

 are very fond of them. Bullfrogs and turtles are also fond of 

 crayfish, and many water birds, particularly the herons, feed 

 upon them. 



The crayfish themselves are rather omnivorous in their food 

 habits. They are scavengers, and are fond of all kinds of 

 meat and soft-bodied insects and larvae. Crayfish also feed 

 upon fish. They will devour any dead fish they can find. They 

 also catch small fish when the latter are placed in an aquarium 

 with them. We have seen them catch them on riffles in small 

 streams, and also in the small streams that run over the 

 ground from the water pipes while we are lowering the ponds 

 at the Hatchery. 



The crayfish caught in the nets with the small fish when we 

 are seining at the Hatchery frequently kill the young fish by 

 catching them in their pinchers, and sometimes become very 

 troublesome. Thus far we have never taken a real good crop 

 of young fish from a pond that had a great lot of big old cray- 

 fish in it. A certain number of them may be all right in 

 breeding ponds. However, we would rather have them in 

 stock and feeding ponds where there are fish large enough to 

 handle them. 



Make Holes in the Banks. 



Crayfish sometimes become very troublesome by digging 

 holes in the banks of the ponds. They also dig holes in the 

 bottom of ponds. In some soils this makes it possible for the 

 water to flow down and seep out through the lower strata or 

 beds of sand and gravel on which the bottom of the pond rests. 

 In sandy or loamy soil it is frequently necessary to puddle the 

 bottom of a pond to make it hold water. In such ponds the 

 crayfish can do much damage by making holes that will allow 

 the water to seep out of the pond and flow away through the 

 porous material that underlies the puddled or true bottom of 

 the pond. 



To Get Rid of Crayfish. 



We know of no easy method of getting rid of crayfish when 

 they once get in a pond. They migrate from place to place, and 

 if they get in one pond they will soon be in all the ponds in the 

 same locality. When they get too plentiful in any of the 

 Hatchery ponds we usually stock such ponds with large Black 

 bass. The bass are very fond of them, and when they once get 



