148 WAITE: TROUT HATCHING AT KNARESBOROUGH. 
From observations taken on the spot, by means of a standard 
river thermometer, it was ascertained that the temperature of the 
water supplied from the bottom of the filter beds was 41°6°, that from 
the reservoir of unfiltered water 45°. Both the supplies run into 
proved to be 44°. From this tank the water runs through each of the 
trays successively and the temperature of the water on leaving the 
last tray was found to have risen to 45°2°, that of the open river at 
the same moment being 46°. The bailiff finds that from about 95 
to 105 days is necessary for the artificial hatching out of the ova as 
deposited in the trays. 
Great care requires to be exercised on every part of the operations, 
not the least important being the daily inspection of the ova with 
a view to discover the presence of a destructive fungus which 
frequently attacks on ae ova, thence spreading to neighbouring 
ova which are ferti t is also necessary to discover and remove 
infertile ova, in dee to lessen as much as possible the grounds of 
the attack of this fungus. 
The young fish are allowed to remain in the zinc trays until the 
olk-sacs are almost absorbed, when they are removed into the 
reservoir of unfiltered water, where they remain for the greater part 
ofa year. By this time the fish have attained the size of a gudgeon, 
and are then transferred into the river, a certain proportion being 
conveyed and turned into the upper reaches whence the spawn was 
first obtained, as a compensation to the Yorkshire Fisheries Board, 
by whose permission the Knaresborough Angling Club is enabled to 
procure the necessary supply of spawn. 
he following table shows the result of visits made to the higher 
reaches of the Nidd during the months of November and December 
last year 
ate. Males. Females. Ova obtained, 
iW. 1k . 24 ie 8 oe 1,000 
ys cen 43 21 300 
” 14 42 32 2,500 
ay a8 14 3 100 
» %I9 4 3 1,000 
99 26 8 5 : 15° 
Pas. 13 8 1,500 
Dec. x I I 15 
” 4 51 19 2,300 
wood 53 30 5,500 
» 8 36 39 9,500 
i 13 13 1,500 
i 27 24 , 
se 24 I2 4,000 
» 4 23 10 1,000 
os 22 9 1,000 
» 18 . 3 5 500 
» 29 6 § 2; 
Naturalist, 
