6 Part III. — Twenty-seventh Annual Report 



In the Firth of Clyde, and in particular in Loch Fyne, the investi- 

 gation into the herring fishery which has been in progress during 

 the last few years was continued, and observations on the tempera- 

 ture of the water and the relative abundance of plankton were made 

 as frequently and regularly as circumstances allowed. This subject 

 is dealt with more fully below. 



Among the researches in progress, but not yet completed, may be 

 mentioned the relation between the salmon fishery and the herring 

 fishery in Loch Fyne, the destruction of immature herrings by sea 

 birds and certain predaceous fishes, the development of decapod 

 Crustacea, and the food of the halibut. 



The Hatching of Plaice. 



During the spawning season of 1908 the hatching of the eggs of 

 the plaice at the hatchery was continued as in previous years. The 

 methods employed have been described fully in previous Eeports, but 

 it may be mentioned that the adult plaice are kept alive in a large 

 tidal pond, the spawning pond, where they shed and fertilise their 

 eggs in a natural way during the spawning season. The eggs are 

 then collected from the water by a large net and transferred to the 

 hatching apparatus, which are of the Dannevig type, where they are 

 retained till they hatch, the larval fishes or fry being also kept in the 

 apparatus till the time when the yolk is nearly absorbed, when they 

 are transferred to the sea at selected places. 



Success primarily depends on having a large stock of breeding 

 fishes in order that as great a quantity of eggs as possible may be 

 obtained. In former years, when commercial trawlers were employed 

 to fish under scientific observation in the Moray Firth and Aberdeen 

 Bay, ample numbers of adult plaice were secured to stock the pond ; 

 but in recent years, as explained in previous Reports, considerable 

 difficulty has been experienced in getting sufficient supplies. By 

 means of the research steamer " Goldseeker," a considerable number 

 of plaice suitable for breeding purposes were brought from the Moray 

 Firth to Aberdeen in the autumn of 1907, and in consequence of this 

 the quantity of eggs made available in the following season was 

 increased, thougli it was still insufficient to work the apparatus to 

 their full capacity. 



The estimated number of eggs removed from the spawning pond was 

 15,332,000, and the number of fry obtained from them was estimated 

 to be about 12,296,000. The first eggs were found on 13th January, 

 and the last on 14th May. The number collected in each month 

 during the spawning season, and the percentages to the aggregate, are 

 shown as follows : — 



Number of Egga. Percentage. 



January, - - - . 146,000 0-95 



February. - - - 3,766,000 24-6 



March, - - - . 7,170,000 467 



April, - - - - 3,420,000 22-3 



May, - - - . 830,000 5-4 



