2o6 BRITISH FRESH-WATER FISHES 



1. The protection of the fertilised ova from ice, floods, 

 and destruction by predaceous animals of many kinds. About 

 the superior results of artificial hatching in this respect there 

 can be no doubt whatever. From 90 to 95 per cent, of the 

 ova laid down may be expected to hatch under careful manage- 

 ment, whereas in the natural beds it is impossible to calculate 

 the proportion that may be devoured or otherwise destroyed 

 during incubation. 



3. The protection of the alevins during the tender period 

 while the umbilical bag is being absorbed, when they are as 

 defenceless as eggs themselves, and in the further stage of fry. 

 In this point also the advantage is all on the side of artificial 

 culture, but the ultimate benefit to the fishery depends almost 

 entirely upon whether the fry are turned loose at once or 

 protected during a second winter until ready to make their 

 migration to the sea. 



4. The certainty of a full and constant hatch of fry inde- 

 pendent of such conditions as scarcity of spawners, severe 

 winters, and other untoward circumstances. In this the 

 advantage certainly is with the hatchery. 



The objections to artificial propagation are as follows : — 



1. The disturbance of the spawning beds by netting the 

 spawners. This is a very serious consideration. Every well- 

 managed hatchery should be provided with the means of 

 taking fish before they go on the redds, impounding them in 

 suitable tanks or pools, where they may lie quiet until ready 

 to shed their spawn. Fish spawning on the natural ground 

 should be disturbed under no circumstances whatever. 



2. The depletion of the natural stock of a river in order 

 to substitute a stock reared artificially, and consequently less 

 capable of encountering the vicissitudes of salmon life. I do 

 not regard this objection as of any weight. The depletion 

 caused by stripping spawners is amply compensated for by the 

 far greater number of young brought safely through the egg, 

 alevin, and fry stages ; and, in the parallel case of hand-reared 



