FISH AND FISHERIES. 151 
The simplest hatching apparatus consists of a series of shallow boxes 
halffilled with sand, and placed at a gradually descending plane from 
first to last. A very small flow of water from a tap into the uppermost 
box, and from that to the others, will keep the water oxydized and 
prevent the development of septic germs. It is found however 
that this arrangement has many disadvantages, and leads to a great 
waste of roe. The uppermost boxes consume the oxygen from the water, 
which by degrees loses the necessary vitality which is required for 
hatching the roe in the lower boxes. The method adopted in Dr. 
Klenertz’s Fish-hatching Apparatus is this :*—Each box is supplied with 
it own stream of water, which is as much mixed with air as possible. 
The water is brought to a large stone trough in which the fish (trout) 
are kept during the summer, until the roe and milt are ready in the 
autumn. The water runs from this stone trough through numerous 
separate pipes to two other large troughs, one of stone and the other of 
wood, the sides and bottoms of which are covered with cement; each of 
these troughs is ahout 12 feet long, 2 broad, and 2 deep. Small gratings. 
in the sides serve as rests for the hatching boxes. These are made of 
sheet-iron well painted in oil colours to prevent rust. They are a foot 
square on the bottom and 5 inches high. They are pierced with two 
rows of fine holes, and on the top there is a grove which is likewise fur- 
nished with fine holes. After the box is filled with clean gravel to the 
height of 3 inches, and on this. the roe is thinly spread. The water 
which supplies these boxes is conveyed through small perpendicular 
tubes each furiiished at the end with a rose so as to separate the 
falling water and bring it as much into contact with the air as possible. 
This water falls over the hatching boxes, and is still further aerated by 
the fine holes in the tops. The exclusion. of much light is essential to 
the success of the experiment, especially of the hatching. The gravel is 
boiled for some time before using, to free it from the spores of plants, 
which are most destructive to the roe. This method has led to the best 
results, and only a small percentage of the ova, are lost. t 
Various modifications of these processes are in operation throughout 
Europe. Until it was adopted in Britain the salmon-fishery was in danger 
of extinction. The fecundity of fish is, well known, but the waste 
was not. For instance, we find according to the late Mr. Frank Buck- 
land, that the amount of ova to each pound of roe was as follows for 
the different fishes mentioned :—Salmon, 1,000 ova to each pound the 
fish weighs ; trout of 1 pound weight, 1,008 ; herring of half-a-pound 
19,840 ; perch of halfa-pound, 20,592; jack of 44 Ibs., 42,840; mack, 
erel of 1 pound, 86,220; sole of 1 pound, 134,466; brill of 4 Ibs., 
239,770 ; turbot of 8 lbs., 385,200; roach of three-quaters-of-a-pound- 
480,000; cod of 15 Ibs, 4,872,000! Yet two-thirds of this or a 
larger quantity is lost under the most favourable circumstances. 
In some respects there is matter for congratulation in this, for 
it would not do to have the seas overrun with cod-fish, however 
* This plan is not selected as the best, but as a convenient instance out of 
many which requires neither expensive buildings, nor apparatus. 
+For a full description of the whole subject see ‘‘Fish-hatching,” by Frank 
Buckland, London, Tinsley Brothers, 1863. A list of other works is given at 
the end of this chapter. 
