CULTURE OF SALMONOIDS AND CRAWFISH. 
377 
exceedingly important article of food in the culture of salmonoids and crawfish, we 
must seek to encourage its development by supplying artificial hiding-places and also 
by feeding it. Especially in the early stages of the establishment, when the bottom and 
sides of the ponds and ditches are not yet covered with plants, it will be well to supply 
such hiding-places (e g., by transferring or planting aquatic plants). Such artificial 
hiding-places for the shrimps may also be provided in the ditches and in the stream 
by digging round holes with an upper diameter of 40 to 50 centimeters (1.5 to 1.9 
inches) and a depth of 20 to 25 centimeters (0.78 to 0.88 inches), at an angle of 45 
degrees toward the bank. These holes should be dug at distances of about 5 meters 
(16 feet), and wherever the ditches widen out they may be scattered more frequently. 
Such holes may also be dug in the channels through which the water flows in and out 
of the basin. 
In these holes are placed branches deprived of their leaves, which (by means of pine 
roots, willow branches, etc.) have been loosely bound together and formed into a sort 
of ball, and which may project over the middle of the hole and its edges, stones being 
put in the inside of these balls to keep them in position. In fig. 8 we see in a broad 
part of a ditch the cross section of two such shrimp holes with the balls of branches 
inserted. The fish and crawfish, when in search of food, can not, on account of their 
size, enter these holes, and the shrimps find sufficient protection in them, and can 
therefore undisturbedly increase in these hiding places. This arrangement, moreover, 
permits a very rapid and simple method of feeding the shrimps, as it will be sufficient to 
throw on these branches from time to time a handful of coarse meat-meal, chopped-up 
fish, frogs, mussels, meat, maggots, etc. It has the further advantage that whenever 
the fish are taken out of the ditches, ponds, etc., the main portion of the shrimps will 
remain alive, because they can retire to their holes, in which some water will always 
remain while the ditches are slowly laid dry. To catch a large number of shrimps 
at any time, it will be sufficient to pull out the branches or balls of branches and shake 
them over a piece of cloth. In newly constructed inclosures the shrimps must, of 
course, be introduced in larger quantities and be evenly distributed. 
The fish or crawfish should not be placed in the water until the shrimps have 
increased considerably and have occupied their holes. It might also be recom- 
mended to give these small crustaceans a short period of protection after each fishing- 
season. The cultivator of salmonoids and crawfish possesses in these holes reliable, 
constant, and abundant sources of food for his fish. In the more stagnant water of 
the ponds shrimp-culture will not be so successful, but even there the above described 
method of promoting the increase of other crustaceans in these ponds will benefit 
the eutire cultivation. 
The supply of natural food for fish, etc., may be still further increased if willows 
are planted close together, each plantation extending from 2 to 2£ meters [6.8 to 8.5 
feet] on both sides of the inclosures. Thereby many insects, especially many different 
kinds of gnats and flies, are attracted, which, owing to the sheltered condition of 
the water, deposit their eggs therein. In order to make this more convenient for 
them, it is recommended to fix widely spreading branches at certain distances in the 
banks in such a manner as to let them rest on the surface of the water. The larvae 
of these insects make an excellent food for fish. The willows, moreover, will furnish 
a habitation for a large number of different kinds of caterpillars, beetles, spiders, 
bugs, etc., which often drop into the water and very considerably increase the food 
supply for the fish. 
