18 FISH FARMING: 



may be two or more series ; but in such case each series should 

 be screened off a-nd a sluice fixed as D D at c. 



Fig. 3 requires a little more explanation. It will, however, 

 be seen that by this arrangement the redds are under abso- 

 lutely complete control. But even in this case I strongly aid- 

 vise you to choose a position where there occurs least risk of a 

 big flood. 



It often happens, though, that such a position is not 

 attainable on an estate ; and, if this be so, an arrangement of 

 redds formed off a river such as here shown should be with 

 care and attention at the critical time quite free from 

 any unfortunate results. A A A A A are the redds ; B B B B B B 

 the falls ; c ig the only screen required ; D D D, D D, D are 

 sluices ; E E is the outlet for debris and surplus water from 

 sluice D D ; E is the main outlet from the surplus water chan- 

 nel F F F ; at E E a contrivance for preventing fish running i.p 

 may advisedly be placed; at E one must be put, or a screen 

 may be put in place of a contrivance, but the latter is much 

 to be preferred, for reasons already stated; F F F is the 

 surplus water channel; G G is the supply channel to the 

 redds ; H is the main outlet from, the redds. In the spawning 

 season the fish will run up at H; the screen, c is then put into 

 position ; the fish are prevented from, running up the channel 

 at E, therefore they mount to the redds. If the fall at llie 

 top end of the redds, at G, cannot be made of sufficient height 

 to prevent fish mounting up it, another arrangement of 

 the supply channel becomes advisable, and this is 

 shown in Fig. 4 and Fig. 5 ; otherwise the fish will 

 mount intoi the channel G G. This latter arrangement is also 

 advisedly adopted where the sluice D is not absolutely proof 

 against fish dropping down stream and over it; indeed, I 

 should always advise its adoption, only that where possible 

 the aeration occurring from a decent fall at G, at the head of 

 the redds, is most beneficial. 



Fig. 4 is a plan of an underground supply to the redds, and 

 Fig. 5 is a section of same through N o. Here again A is the 

 top redd, the width of which from p to H is purposely shortened 



