94 



Part III. — Ttventy -sixth Annual Report 



again to near the freezing point on 22nd and 23rd February. The 

 temperature of the water in the hatching apparatus between 26th 

 February, when eggs were first obtained, till the close of the season, 

 varied between 331 F. (on March 9th) to 52 F. on 15th May. The 

 specific gravity' of the water in the spawning pond remained tolerably 

 uniform throughout the hatching season, varying between 27*0 and 

 27-8. 



The number of the eggs of the plaice collected from the spawning 

 pond and the number of fry hatched out and placed in the sea in the 

 various years since the hatchery was established at the Bay of Nigg are 

 as follows : — 





Eggs Collected. 



* Fry Produced. 



1900, 



43,290,000 



31,305,000 



1901, 



65,377,000 



51,800,000 



1902, 



72,410,000 



55,700,000 



1903, 



65,940,000 



53,600,000 



1904, 



39,600,000 



34,780,000 



1905, 



40,110,000 



24,500,000 



1906, 



7,486,000 



4,406,000 



1907, 



1,627,000 



1,282,000 





335,840,000 



257,373,000 



The reason for the decline in the hatching work in the last two years 

 was referred to in the last Annual Report, when the operations in 1906 

 were described. The quantity of fertilised eggs depends upon the 

 number of adult fishes in the spawning pond, and hitherto the stock of 

 spawners was obtained by the use of a trawler which was permitted to 

 fish in the bays of the Moray Firth and in Aberdeen Bay for the 

 purpose of procuring a supply, all the plaice which were suitable for the 

 hatchery being brought ashore in tubs, the remainder of the catch 

 becoming the property of the owner of the trawler as recompense for 

 the use of his vessel. This arrangement was interrupted at the end of 

 1905, as explained in last Report, and such plaice as have been since 

 obtained for the hatchery have been brought ashore from the Moray 

 Firth by the " Goldseeker," the vessel employed in the international 

 fishery investigations, but the supply has not been adequate for the 

 work. Plaice of the kind required are only to be caught in any 

 quantity on the inshore grounds, where trawling, except for scientific 

 purposes, is prohibited. Under present circumstances it is not possible 

 to get sufficient supplies from the ordinary commercial trawlers working 

 on the offshore grounds in the North Sea. As a rule, the quantity of 

 plaice obtained by them on any single voyage is small, and it would 

 require many expeditions to obtain a sufficient number for the hatchery. 

 The fish obtained in this way would, moreover, have to be purchased at 

 their market value, and the cost could scarcely be borne by the present 

 vote for scientific investigations. 



The expense incurred in dealing with a small quantity of eggs is very 

 little less than that of dealing with a large number. At present the cost 

 of the hatching work is very moderate, and is estimated not to exceed 

 about .£80 per annum. This is owing to the fact that the work is 

 carried on in conjunction with that of the Marine Laboratory, no addi- 

 tional staff being required, the attendant (Mr. George Walker) being 

 also able to undertake the care of the hatchery, the expenditure on the 

 hatchery representing mainly extra coals, food for the fishes, etc. 



