of the Fishery Board for Scotland. 



121 



the number of the adult fishes furnishing eggs, and therefore of the 

 eggs collected, was considerably under what it was in 1903. As pointed 

 out in previous reports, a certain number of the plaice confined in the 

 pond die each year, and this loss is ordinarily made up by a renewed 

 supply of living adult fishes in the autumn, which are obtained from 

 the trawlers employed for scientific purposes in Aberdeen Bay or the 

 Moray Firth, the vessels being provided with large tubs for the 

 collection of the fish, and a constant circulation of water maintained until 

 port is reached. In the autumn and winter of 1903 the same practice 

 was followed, but it was found that large adult plaice, suitable for the 

 hatchery, were exceedingly and unusually scarce, and thus the stock in 

 the pond was only partially replenished. 



The total number of eggs collected from the spawning p@nd through- 

 out the season was 39,600,000, as compared with 65,940,000 in the 

 previous year. Most of them, as is usually the case, were obtained in 

 March, which is the chief spawning month of the plaice. The numbers 

 collected in the various months, and the percentages on the total 

 number, are given in the following table, which also contains for com- 

 parison the corresponding monthly percentages for the previous season 

 in 1903 :— 



Number of Eggs Percentage, Percentage, 



Collected. 1904. 1903. 



January, - 660,000 P6 0'3 



February, - 10,320,000 26-1 18-0 



March, - - 22,040,000 55-7 56'2 



April, - - 6,580,000 16-4 24-1 



Mav, - .. .. 1-3 



It will thus be seen, as above indicated, that spawning was, on the 

 whole, a little earlier in 1904 than in 1903, nearly 28 per cent, of the 

 aggregate number of eggs being collected before March in the former 

 year, as compared with 18 per cent, in the same period in the latter year. 



The estimated number of fry which were obtained from the eggs 

 amounted to 34,780,000, and they were liberated in seven lots at 

 various dates in March, April, and May, off Aberdeen Bay, a fishing- 

 yawl being employed for the purpose. 



Particulars as to the collection of eggs from the pond and the libera- 

 tion of the fry will be found in the tables which are appended. 



The expense of the hatching operations as carried on at the Bay of 

 Nigg is small, compared with the number of fry produced. This is 

 owing to the fact that the hatchery is worked in conjunction with the 

 Marine Laboratory, for which pumping operations are required 

 throughout the year. The annual expenditure that may be ascribed to 

 the hatching work is about £100, the principal items being the main- 

 tenance of the apparatus, food for the fishes, and extra coals. 



The hatchery was visited by delegations of fishermen sent for instruc- 

 tion by the County Councils of Aberdeenshire and Argyllshire, to whom 

 a series of demonstrations was given. 



[Tables. 



