Trout Rearing Ponds Boxes And Hatching Trays
Having decided upon a suitable spot, the amateur must now proceed to
make his ponds. Whether he derive his water supply from a spring or from
a stream, the amateur had better bring it into his ponds through a pipe.
A three-inch pipe will be large enough for a pond thirty feet long,
three feet wide, and two feet deep at the deepest part. It is a good
thing for the water to fall, some inches at any rate, through the air
efore it reaches the pond, and in a series of ponds with only one
supply, the water should flow through an open trough with stones and
other impediments in it, between the ponds. The ponds may be lined
entirely with brickwork faced with cement, and in this case the sides
should be made perpendicular. The cement should, however, be exposed
freely to the action of the running water for a couple of months at
least before any ova or fry are introduced.
Another plan, and a simpler and less expensive one, is to face only the
ends of the ponds with brick and cement work, carrying the brickwork
into the earth on each side, as shown in Fig. 1. In this case the sides
of the ponds should be slightly sloped as shown in Figs. 2 and 3. It is
advisable if possible to make the outlet at the level of the bottom of
the pond, if the pond is lined with cement, but if the pond is only
cemented at the ends, it is better to have one in mid-water or even near
the surface. As I have said before however, an outlet should be made at
the level lowest part of the bottom, so as to facilitate the emptying of
the pond. The pond should however be made shallower at the lower end.
Fig. 2 shows a section of the upper end, and Fig. 3 of the lower end of
such a pond.
The open trough between ponds in a series should be at least three yards
in length, but it is better if not straight. Stones and gravel should be
put in these troughs in order to make the water as rough as possible,
and if some fresh-water shrimps can be introduced so much the better.
If the water is taken from a stream, a leaf screen must be placed at
some distance in front of the inlet. This may be made of a hurdle
fastened to strong stakes sunk into the bed of the stream. The opening
of the inlet should be at least double the size of the sectional area of
the pipe through which the water is carried to the ponds, and should be
some distance, a couple of feet if possible, below the surface of the
water. It is a good thing to put a wire cage over the inlet, and under
this a perforated zinc screen is necessary. The inlet from the stream
should be so placed that it is easy to get at and clean. The best form
of covering for the inlet into the pond I have seen, is a zinc cylinder,
the base of which fits over the end of the inlet pipe. The part of this
cylinder, which projects 18 inches beyond the pipe, is perforated, as is
also the flat end. This can easily be taken off and cleaned, and breaks
up the water, making it fall into the pond like a shower bath, causing
considerable aeration.
The inlet from the stream should have a trap with which the water may be
shut off, as also should the outlet from the pond. When the cylinder on
the inlet into the pond is taken off for a minute or so to be cleaned
out, both these traps must be closed. This lessens the chance of any
creatures likely to do harm getting in during the cleaning. The
perforated zinc screen at the inlet from the stream will probably stop
any such creatures, but too great care cannot be exercised, and it is
always best to be on the safe side.
Movable covers of netting over the ponds are most certainly advisable,
particularly if the rearing ponds are in an unfrequented spot near a
stream. On one occasion I caught four kingfishers during a period of
three weeks, all of which had in some way got under some herring net,
which was pegged out carefully over a rearing pond containing trout fry.
I never found out how they got in, but once in they were unable to
escape.
Ponds such as I have described are of course for the fry when they have
reached a certain size, and have already begun to feed well. Other
appliances are necessary for hatching out the ova and for the young fish
when first hatched. A very good apparatus may be made from a champagne
case. This should have large square holes sawn through each end, leaving
enough wood to ensure strength and solidity to the box. The box should
then have two coats of asphalt varnish, and the square apertures covered
with fine perforated zinc. A still better box may be made at a small
cost. This consists of a box with a wooden bottom and perforated zinc
sides which are supported by a stout wooden frame.
Beyond these boxes all that are required are some perforated zinc
hatching trays. These should be 1-1/2 inches deep. They are very easily
made, and the ova hatch out well in them. Though ova sometimes hatch out
very successfully even when piled up in two or three layers, it is safer
to have them in a single layer. The trays should be suspended in the
boxes, and the boxes in the ponds close to the inlets, so that a good
current of water may flow through them. The bottom of the boxes should
be covered with a thick layer of gravel, but the trays are to be used
without gravel. It is advisable to have as much grass as possible round
the ponds, and such trees as willows and alders should also be planted
round them. Willows and alder sticks planted in the early part of the
year come into leaf in the same spring, and afford shade to the young
fish in the summer. Some suitable weeds should also be grown in the
rearing ponds. Water-cress, water-celery, water-lobelia, starwort, and
water-milfoil, are all good. They should be arranged, however, so as to
prevent as much as possible the little fish finding hiding places, and
it is for this reason also that I have recommended slightly sloping
banks when the sides of the ponds are not made of cement. The weeds
should be planted some time before the little fish are turned out of
the boxes.
Finally, I must caution my readers again on one or two points before I
leave the subject of the hatching trays, rearing boxes, and ponds.
Enamel, varnish, or charr all woodwork thoroughly, leaving no speck of
wood bare and no crack open. Let the water run through and over all your
ponds and apparatus for as long as possible before you begin
operations.