180 Part LII.—Twenty-first Annual Report 
IV.— REPORT ON THE OPERATIONS AT THE MARINE 
HATCHERY, BAY OF NIGG, 1902. By Dr. T. Wemyss 
Futron, Scientific Superintendent. 
' In previous reports the methods and arrangements in connection 
with the hatching of plaice have been described, the principal conditions 
of successful working being the providing of a good stock of adult fishes 
to furnish the spawn, and an abundant supply of pure sea water of 
proper density for the hatching apparatus. . 
Since the erection of tie hatchery on its present site in the autumn 
of 1899, it has been found possible, by means of the large, sunk, tidal 
pond, to keep a breeding stock from one season to another instead of 
renewing it yearly, as was previously the case. Under the former 
system it took a considerable time for the fishes to become accustomed 
to confinement, and many of them did not spawn, bet retained their 
eggs, and died in an egg-bound condition, and thus the quantity of 
fertilised spawn obtainable from a given number of fishes was materially 
reduced. 
At the end of the hatching season in 1901 the number of plaice 
remaining in the pond was found to be 767, most of which continued 
to thrive during the summer and autumn. To these others were added 
in the winter, the fishes being procured on board steam-trawlers provided 
with large covered tubs, through which a constant circulation of water 
was maintained, and which were transferred to the hatchery and the 
fishes placed in the pond. At the end of November 21 were obtained 
from Aberdeen Bay, in December 345 from Burghead Bay in the 
Moray Firth, and early in January 120 from off the coast of Caithness. 
As is always the case, a considerable number of the newly-introduced 
fishes succumbed later, chiefly in consequence of injuries and abrasions 
received in the course of capture by the trawl-net, and partly as the 
result of abrasions in the tubs, where they were sometimes confined for 
several days. The breeding stock for the season was estimated to 
number about one thousand plaice of both sexes. 
During the latter part of January the temperature of the water in 
the pond was rather lower than usual, and few eggs were observed 
to have been shed until the early part of February. The first collection 
was made from the spawning-pond on the 8th February, when about 
20,000 eggs were obtained, and on the next two days about the same 
quantity. Owing toa hard frost occurring on the following days the 
temperature of the water sank and spawning was checked, and no 
further collection was made until the 17th, when 40,000 were obtained. 
In the first half of March the number of eggs greatly increased, over 
two millions, and occasionally nearly three millions, being taken from 
the pond daily, the aggregate up to the 16th March being over 
38,000,000. After this period the number diminished in March and 
still more in April, and the last collection was made on the 25th of 
April, viz. 20,000. 
During the season the large total of 72,410,000 eggs were obtained, 
or about seven millions more than in the preceding year. It is believed 
that this large total was mainly owing to the thorough acclimatisation 
of the majority of the spawners during the year or more in which they 
were kept in the tank. It may be said that the fishes in the course of 
time become very tame, instead of withdrawing themselves and skulking 
at the bottom of the tank as is the habit with those newly introduced. 
They frequently swim about the surface at the sides of the tank in 
