Buck. — Catch Basin Ponds 69 



tunately this can be done by locating the trout in ponds 

 having a drainage outlet other than to the ponds below. 

 The arrangement is such, however, that it is necessary to 

 supply part of the trout ponds through the hatchery or 

 through other trout ponds or pools. No harm appears to 

 result from this except the risk of communicating dis- 



| ease, but this risk is now an important matter and an 

 effort is being made to effect such a rearrangement that 

 each trout pond shall have its own supply, or better still 

 that each shall have two independent supplies. This lat- 

 ter is now possible since the flow of another and larger 

 spring has been brought to the station. 



It is worth considering whether repeated use of water 

 has any causal relation to the appearance of the disease, 

 which has for years been on the increase in hatcheries 



j and the control of which is now a problem of prime im- 

 portance. But, however this may prove, it is reasonable 

 to avoid risk of infection so far as practicable and for 

 this reason the series or catch-basin plan seems undesir- 

 able for trout ponds. 



It is also objectionable because aeration is less in the 

 lower ponds unless there is sufficient difference of level 

 to admit of a drop through the air from pond to pond, 



j which is not the case here in most of the series. The 

 other sorts of fish do not appear liable to infection nor to 

 miss the fresh aeration and, the disadvantages not apply- 



i ing, it remains to consider what advantages the catch- 

 basin system offers in their case. Two have been re- 

 ferred to above: (1) economy of water and (2) raising 

 of temperature, the latter being an advantage not only 

 directly to the fish but indirectly by promoting the in- 

 crease of the minute life necessary for their food. The 

 catch-basin system offers the means of saving and dis- 

 seminating this. Not that the diffusion from pond to 

 pond is likely to be great at most times, but because it is 

 practicable, when the ponds are drawn, to float it down 

 m great quantity to the pond below. This requires be- 

 ginning with the lowest pond and working up the series. 

 Although the pond fish are more adaptable than trout, 



