FISHES AND MANKIND 409 



culture forms a flourishing industry: it has been introduced 

 with some success into the United States, but has long died out 

 in England. The fish farms in Germany are often of consider- 

 able size, some of them being six or seven thousand acres in 

 extent. The Carp is a very hardy fish, can be bred and reared 

 to maturity under all kinds of conditions, requires no costly 

 food, consuming refuse and other natural products which are 

 otherwise useless, grows rapidly, and, if properly cooked, has a 

 deUcate flavour. Rapid growth to a marketable size is essential 

 to a profitable industry, and modern growers have succeeded 

 in producing races that grow to an average weight of two and 

 a half pounds at the end" of their third summer, and in some 

 tropical countries the rapid growth is even more striking. 



The second type of pisciculture, namely, the artificial propa- 

 gation of fishes for stocking purposes, is carried on extensively 

 in various parts of Europe and America. Trout lend themselves 

 particularly well to this form of cultivation, and can be profitably 

 hatched in special receptacles. In our own country great 

 advances have been made in this industry with the marked 

 growth which has taken place in the volume of angling, and 

 every Trout stream of any value or note is restocked from time 

 to time as a matter of course. In the United States the Brook 

 Trout, Black Bass, and to a lesser extent some of the Sun-fishes, 

 are cultivated in huge numbers, the Brook Trout also being 

 reared to a fair size in ponds. By feeding these fishes on a diet 

 of slaughter-house offal, in addition to the natural food in the 

 ponds, they can be made to grow two or three times as fast as 

 in the wild state. The actual process of artificial fertilisation is 

 very simple, the ripe female fish generally being "stripped," 

 the eggs being pressed from the body into a vessel into which 

 a httle of the milt of the male is introduced. When fertilised, 

 the eggs are either distributed at once to the waters which have 

 to be stocked, or they are placed in special receptacles provided 

 with a suitable stream of water until the fry are hatched. 

 These may be planted at once, but do not always flourish, 

 and it is advisable to stock the waters either with unhatched 

 eggs or with fry which have been reared for a period in the 

 hatcheries until they are active and hardly. 



The ease with which the natural development of the ova can 

 be retarded by storing them in ice makes it possible to introduce 

 certain species of fish into new countries or even into fresh 

 continents. Trout were taken into New Zealand from England 

 as early as the late 'sixties, and this country now boasts the 



