256 Part III. — Twenty -fifth Annual Report 



v.— REPORT ON THE OPERATIONS AT THE MARINE FISH 

 HATCHERY, BAY OF NIGG, ABERDEEN, IN 1906. By 

 Dr. T. Wemyss Fulton, F.R.S.E., Scientific Superintendent. 



In the Annual Report for last year* an account was given of the 

 arrangements at the hatchery and the alterations which had been 

 made, togetlier with a number of plates showing the hatchery, ponds, 

 etc. It need only be said here that the adult plaice from which the 

 spawn is obtained are confined in a large tidal pond, where they are 

 kept throughout the year and fed on mussels. At the spawning season 

 the eggs are shed into the water of the pond, from which they are 

 collected by a large gauze net and transferred into the hatching 

 apparatus. They are maintained in the appaiatus until the young 

 hatch out, the length of this period depending dii'ectly upon the 

 temperature of the water. At the commencement of the spawning 

 season, when the temperature of the water is low, the duration of the 

 period of incubation is on the average about three weeks ; at the end 

 of the seiison, when the temperature has risen considerably, it occupies 

 about a fortnight. The larval fishes, after they aie hatched out, are 

 kept in the apparatus for several days, until the yolk-sac is partly 

 absorbed, and they are then placed in the sea. 



It is estimated that, including both periods — the time of incubation 

 of the eggs and the period during which the larvae are retained — 

 protection is conferred upon the eggs and larvae for about half of the 

 time that naturally elapses from the spawning of the eggs until the 

 complete transformation of the larval fish, when the charactei'istic 

 adult form and habit is assumed. 



The success of the hatching operations depends very largely upon 

 two circumstances — an adeqviate supply of eggs and a sufficient supply 

 of pure water. In order to obtain a large supply of eggs it is necessary 

 that the number of adult fishes in the spawning pond should be large. 

 Hitherto the method adopted of obtaining the adult brood stock was as 

 follows : — By the authority of the Boai-d a steam trawler was permitted 

 to trawl within the territorial waters, and more particularly within the 

 Moray Firth and Aberdeen Bay. By an arrangement with the owners 

 of the tiawler and the skipper the hatcheiy attendant accompanied the 

 vessel on such occasions, taking with him and fitting up on deck a 

 number of large wooden tubs, through which a constant circulation of 

 sea water was maintained by means of the donkey-pump. Into these 

 tubs the plaice which were selected from the catches brought on board 

 were placed, and when the vessel returned to Aberdeen they were 

 transferred in tanks to the hatchery pond. The plaice required for the 

 purposes of the hatchery were thus obtained gratis, the rest of the 

 catch of fish being the property of the owners, and regarded by them 

 as sufi&cient compensation for their trouble. 



By the method described the stock of adult plaice at the hatchery has 

 been maintained since the beginning of the work at Aberdeen, for 

 although a large proportion of the stock of one season survives to the 

 next, there is always a considerable loss which requires to be made up 

 each 3^ear. Unfortunately, as mentioned in last Annual Report, the 

 trawler which was engaged in this work at the beginning of December, 

 1905, was stranded in Aberdeen Bay, and owing to the loss of life 

 occasioned thereby the Board have thought it right to refrain from 

 making use of such vessels for inshoie work. In consequence of this 

 the stock was not renewed, and the supply of spawn, as mentioned 



* Twenty-third Anmial Report, Part III., p. 108. 



