262 Part III. — Tiventy-second Annual Report 



V. — REPORT ON THE OPERATIONS AT THE MARINE 

 HATCHERS, BAY OF NIGG, ABERDEEN, By Dr. T. 

 Wemyss Fulton, F.R.S.E., Superintendent of Scientific 

 Investigations. 



During the season of 1903 the operations on the hatching of plaice 

 were continued on a considerable scale as in previous years, and under 

 the same conditions as are described in preceding reports. It need only 

 be stated that the supply of fertilised eggs is obtained, not by stripping 

 the ripe fishes of their eggs and milt, as is done in some other marine 

 fish hatcheries, but by retaining the fishes from season to season in a 

 large tidal pond, feeding them, and at the spawning season simply 

 collecting the eggs from the water by appropriate means, and trans- 

 ferring them to the hatching apparatus. For this method, a large 

 retaining pond is necessary, and the one constructed at the Bay of 

 Nigg has answered its purpose admirably, the fishes remaining in it 

 throughout the year in good health and supplying their eggs at the 

 proper period with a minimum of trouble to the attendants, and with 

 good results in regard to the success of incubation. 



One of the consequences of this system which contrasts with the 

 condition at Dunbar, where the fishes were merely retained in the pond 

 for some time before the spawning began, is that spawning goes on for 

 a much longer time than used to be the case under the former system. 

 It begins earlier and may continue longer, the dates varying with the 

 temperature to some extent, but the extent of the season is always 

 greater. Thus at Dunbar the collection of eggs did not as a rule com- 

 mence till March, the principal reason being that the fishes had not had 

 time to become accustomed to their restraint in confinement after being 

 placed in the pond, and they retained their eggs instead of spawning in 

 a natural way, very often with fatal results, as described in previous 

 reports. In point of fact they did not spawn until they had become 

 accustomed to the conditions in which they were placed. The respective 

 dates for the beginning of the spawuing at Dunbar and at the Bay of 

 Nigg are as follows : — 



9th March 



to 



8th May 





60 days 



23rd March 



i) 



23rd May 





61 



55 



8th March 



n 



8th May 





61 



55 



22 nd February 



? j 



11th May 





78 



55 



15th February 





7th May 





81 



55 



10th March 



55 



29th April 





50 



11 



10th March 



11 



5th May 





56 



55 



22nd January 



55 



2nd May 





100 



55 



8th February 



55 



25th April 





76 



55 



23rd January 



55 



16th May 





113 



55 



It will be observed that the mean duration of the spawning process 

 at Dunbar owing to this delay in its commencement was sixty-five days, 

 while at the Bay of Nigg the mean duration has been eighty-six days, 

 or twenty-one days longer. In the first season at the Bay of Nigg the 

 hatchery was not ready in time, and in the third season the beginning 

 of spawning was delayed by cold, though the termination, which was 



