252 
THE TROPICAL 
AGRICULTURIST. [Oct. 1, 1902. 
the light. It is a point of the greatest importance 
that care shouLl be taken not to cut the weeds in 
the spring until after coarse fish have spawned, 
and the fry have become large enough to "flee awa' " 
on the approach of the knives and pi'.ddle wheels — 
the latter, 1 think, more disturbing than the former. 
The makers of the machine, I notice, recommend the 
cutting of weeds just before they reach the surface, 
and to cut them again and again throagbout the 
season in order that the leaves may never breathe, 
asserting that if this is done they will become so 
weakened that they will gradually die out. This 
process, however, may mean the almost total destruc- 
tion of one year's brood of coarse fish. Land agents 
and others who have the management of these matters 
should certainly make themselves acquainted with 
the times at which the various fish in the waters 
on their estate spawn, and Swatch the batching of 
the eggs and growth of fry in order to ascertain 
when the weed cutting may be carried out without 
injury to the fishery. John ^Bickekd^ke. 
-Jbield, July 26. 
PISCICULTURE. 
Now that interest is taken in the East anent the 
iniportaUon of trout ova from Home with a view to 
the introduction of that game fish to Ceylon, the 
Doon, the Neilgherries, and Kashmir, it may not 
be out of place or devoid of interest for us to give 
a short resume of the necessary process and period 
of incubation. This we are enable to do through 
tliecourtesy ofafriend, an expert, who hasturnished 
us with a lengthy communication regarding 
the acquariiim and exhibit of hatching apparatus 
at the international Exhibition now being held at 
Cork. From this letter we are enabled to produce 
the following article :— 
" As most people are probably aware salmon or 
trout designed to supply ova for artificial pro- 
pagation are caught some little time before the 
breeding season, and impounded in small enclosures 
where they can be kept under observation. The 
males, which can easily be distinguished by the 
colour of their bodies and the shape of tlie lower 
jaw, are separated from the females, and the 
latter are divided according to the time which 
appears likely to elapse before they are ripe; 
While ripening, the spawn is held in the tissue 
of the roe or ovary > but when thoroughly ripe 
the ova becomes detached and are loose in tlie 
general body cavity. This process completely 
alters the appearance of the fish. A hen fish 
with spawn not yet ripe is of compact form and 
firm to the touch, but once the ova are ripe and 
detached, if the fish be held up by the tail, the 
ova falling away to the front eti'l of the abdomen 
cause the shape of the fish to "bag" in most 
unmistakable manner. The hen fish is now 
ready for "stripping." The operator holds her 
tali downwards, over a pail or can, and 
very gently presses the lower side of the body. 
After a few kicks by way of protest, not unnatural 
under the circumstances, she begins to yield her 
eegs in a continuous stream, her quota being 
about eight hundred to every pound of her weight. 
Once " stripped " she goes back to the water 
none the worse for having been artiftcially relieved 
of all family cares. It is then the turn of the male, 
and when enough of his contribution has been 
poured on to the eggs, the latter are stirred round 
and round with the hands, and then covered with 
water. Fertilization is rapidly effected, and after 
an interval the eggs are washed and laid in the 
jyiatohin^ trays, Witb leaaonable ceiire mi gentle 
treatment absolutely no harm is done to the 
parent fish ; but artificial progagation is only too 
often brought into disrepute by ignorant and 
clumsy operators, who wrench the spawn 
from the bowels of the fish without know- 
ing or caring whether it is ripe or not. A 
big fish, even if quite lipe, is not too easy to 
handle, and in such cases resort may be had to the 
"straight waistcoat" exhibited at Cork. It is 
used by Mr. Fitzherbert in his hatcliery (perhaps 
the best appointed in Ireland) on the Boyne, in 
which a million and a quarter salmon fry were 
hatched last season. 
Around the walls of the Irish Exhibition 
building is arranged a series of hatching- 
boxes as used at the principal salmon 
hatcheries in European and America. A 
number of these are fitted with water-supply and 
drain, but, of course, contain no ova, as no salmon 
or trout could be induced to postpone their family 
arrangements for the convenience of visitors to 
the Exhibition. Indeed, the few thousand rainbow 
ova which were hatched in the watercourse of 
the trout-farming exhibit in the grounds were 
probably the very last clutch of the season. 
At Cork the apparatus, although entirely practical 
in installation, is displayed in such a nianuer that 
all the details can be seen. In addition to those 
from other nurseries, incubating and hatching 
boxes are exhibited from Herr JafFe's hatchery 
at Sandfort in Hanover. The incubating 
bos, filled with boat-shapped trays of wood and 
coarse perforated zinc, will accommodate 24,000 
ova, until the eye of the embryo can be seen. The 
coarse zinc of the trays does away with the neces- 
sity for a filter, and as the sedin\ent can readily be 
shaken through to the bottom of the box, where it 
does no harm. When the eggs are "eyed" — (that 
is when the eyes of the embryo can be seen 
through the shell) —they are best transferred to 
the "hatching-box," with narrower trays fitted 
Avith finer zinc ; or the coarse trays in the 
'incubating box' may be replaced by others of the 
same size fitted with No 9 ziuc : but Herr JafFe 
prefers the narrow box on account of the greater 
concentration of water. The 'incubating-box,' 
although certainly desirable is not absolutely 
indispensable, as the 'hatching-box' can be used 
for the whole process. Once 'eyed,' the ova are 
so hardy that the trays can be lifted bodily out of 
the water and all sediment washed away by the 
use of a garden syringe. Hatching takes place 
about twelve weeks after fertilization in the case 
of salmon, which spawn mostly in December and 
much sooner with rainbow trout which as a rule do 
not spawn much before March. In the case of 
salmon fry, much trouble and expense can be 
saved by using the 'floating redd,' another of Herr 
Jaffe's devices. One of them (in which the young 
rainbows were hatched) can be seen in the 
watercourse. It is simply a floating box with 
zinc sides and accommodation for the trays. The 
"redd" for practical purposes would be moored 
in the natural stream in which it was intended 
to ultimately liberate the fry. Eggs, taken from, 
the "incubating-box" as soon as "eyed," are 
placed on the trays of the "redd." Here indue 
course they hatch, and when the babies are 
about six weeks old they are allowed to escape 
through the door at one end of the "redd," a:io 
seek their own way to fame and fortune. 
Trout intended for farming purpose are hatched 
at Herr Jafl"e's establishment in " hatching- 
boxeSf" and transferred when about ten days oU 
