FISH AND FISHERIES. 151 



The simplest liatching apparatus consists of a series of shallow boxes 

 half-filled 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 oxydizcd 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 about 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 furnished 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, f 



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 Avaste 

 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 half-a-pound, 20,592; jack of 41 lbs., 42,840; mack, 

 erel of 1 pound, 86,220 ; sole of 1 pound, 134,466 ; brill of 4 lbs., 

 239,770 ; turbot of 8 lbs., 385,200 ; roach of three-quaters-of-a-pound- 

 480,000; cod of 15 lbs., 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. 



