PISCICULTURE. 351 



stones ; while for the salmon species a bed of gravel in 

 running water would be required. 



Remy, a poor French fisherman, was the first to in- 

 troduce artificial hatching into Europe, being led to his 

 invention by observing the immense destruction of the 

 eggs and young by various enemies in nature. He 

 simply enclosed the eggs, mixed with the milt, in zinc 

 boxes perforated with holes, which were then sunk in 

 the river until the eggs were hatched. At present a 

 number of shallow troughs are usually employed, ar- 

 ranged side by side, and at gradually-increasing ele- 

 vations; water flows through the whole series; this 

 arrangement permits the hatching of eggs of different 

 dates to be conducted simultaneously, and the separation 

 of spawn of different ages. 



When the eggs are hatched, the spawn must be care- 

 fully fed, the food, of course, depending on the species ; 

 young trout and salmon thrive well on the larvae of 

 insects and on smaller fish. 



Pisciculture consists not only in supplying streams 

 and lakes with eggs and young fish under the most 

 favorable conditions; it includes also the precautions 

 which must be observed to fully populate large rivers. 

 At certain seasons of the year various fish ascend the 

 rivers for spawning, and everything that may pre- 

 vent or interfere with their free running up and down 

 must be carefully avoided. Dams in rivers are effective 

 barriers to the running, and laws usually require that 

 fish-ways or fish-ladders shall be provided by which the 

 fish may ascend, jumping, as they easily do, from one 

 step to the next. 



Among the fish that run up the rivers we may mention 

 shad, salmon, sea-trout, sturgeons, and eels. During 



