134 How to obtain tt. 
outlet spouts when it is desired to increase the depth of the water, 
and pieces of either wood or slate will be found very useful for 
the purpose. Both inside the hatchery and outside in the 
raceways, they are often very useful indeed. A trap box should 
be placed below the spout of the last hatching box in each set. It 
does not matter how small it is, but one side should be of 
perforated zinc, to within say an inch of the bottom. Through 
this box the water should pass before it is allowed to flow into the 
gutter that carries it off. The object of these trap boxes is to 
catch any fish that may be escaping, and they play a much more 
important part in the working of a hatchery than many persons 
would suppose. 
I have more than once been told by one of my friends that 
his fry were decreasing in numbers, and he could not tell what 
was taking them. On my suggesting that they might be escaping, 
the idea would not be entertained for a moment. Impossible! 
When my friend, acting on my suggestion, had placed a trap box 
below his outlet spout, he soon found out where the fish were 
going. A few hours would reveal the fact that a dozen or more 
had escaped from the box above during that short time. Ona 
search being made for the crevice through which they had 
escaped, it would be very difficult to find it, and when found my 
friend would hardly be convinced that the little fish could possibly 
have escaped through such a small aperture. Even in a well- 
ordered hatchery there is always a liability that some such 
occurrence may take place, and it is better therefore to be 
prepared for it. With these traps in use such a leakage would be 
detected at once. 
There is another very important accessory to the hatchery 
also, and that is a catch pool. It consists of a pool or pond 
outside the hatchery, in any convenient situation. It may be near 
or at a little distance, but it is at least better to have it a few 
yards away, so as to get the advantage of having a raceway leading 
to it. It may be made of any convenient shape, but for practical 
purposes a long and narrow pond suits best. Some fish will be 
picked out of the hatchery boxes occasionally, apparently nearly 
dead. They are at least‘in such a plight that any fish culturist 
would condemn them. Do not throw such away, but as long as 
