6 



Part III. — Twenty-sixth Annual Report 



pursue the observation? on the temperature of the water and the 

 abundance of plankton or floating herring-food until the fishery 

 improves, so as to bridge over the period of depression, which 

 unfortunately still continues, and to ascertain whether the scarcity 

 of herrings was related to one or other of these conditions. A fuller 

 statement on this investigation is given below. 



The Hatching of Plaice. 



In the season of 1907 the hatching of the eggs of the plaice at 

 the Bay of Nigg Hatchery was continued as in previous years, but 

 owing to the fact that the supply of the spawning adults was the 

 lowest since the work was commenced, the number of the fertilised 

 eggs collected from the spawning pond, and consequently the 

 number of fry obtained and planted in the sea, was the lowest for 

 any year. Although the capacity of the spawning pond allows of 

 much more than a thousand plaice being retained in it with ease, 

 only 87 fishes, including males and females, were available for 

 the supply of fertilised spawn. The cause of the decrease was 

 the difficulty of obtaining supplies of adult fishes. Hitherto the 

 stock w T as 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 securing a supply, all the plaice which were suitable 

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

 the fishes taken becoming the property of the owner of the trawler 

 as recompense for the use of the vessel. This arrangement was 

 interrupted at the end of 1905, as explained in last Report, the 

 plaice since obtained for the hatchery being brought ashore by the 

 " Goldseeker," the vessel employed in the international fishery 

 investigations. 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 com- 

 mercial trawlers working on the offshore grounds. The quantity 

 of plaice obtained by them on any single voyage is, as a rule, 

 small, and it would require many expeditions of the kind to 

 procure an adequate stock, and, as the fish would require to be 

 purchased at their market value, the cost would be very consider- 

 able. 



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

 pond in the course of the season of .1907 was estimated at 

 about 1,627,000, as compared with 7,486,000 in 1906 and over 

 40,000,000 in 1905. The estimated number of place larvae, or fry, 

 obtained from them and " planted " in the sea on the neighbouring 

 parts of the coast of Aberdeenshire was 1,282,000, the loss in 

 incubation amounting to about 21 per cent. Owing to the small 

 numbers of fry that were at any one time available, it was 

 not thought to be desirable to incur the expense of transporting 

 them to the northern parts of the coast as in former years, as was 

 requested by the fishermen of the localities. The number of eggs 

 and fry dealt with since the work was begun at the Bay of Nigg is 

 shown in the following Table : — 



