of the Fishery Board for Scotland. 



93 



IT.— REPORT ON THE OPERATIONS AT THE MARINE FISH 

 HATCHERY, BAY OF NIGG, ABERDEEN, IN 1907. By 

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



In the season of 1907 the hatching of the eggs of the plaice was con- 

 tinued as in previous years, but owing to the fact that the supply of 

 spawning adults was the lowest since the hatching work was commenced, 

 the number of fertilised eggs collected from the spawning pond and the 

 number of fry obtained and planted in the sea were the lowest for any 

 year. Although the capacity of the pond would allow of considerably 

 over a thousand plaice being retained in it, the number which was 

 available for the supply of fertilised eggs was only 87. The reasons for 

 this are referred to below. 



The first eggs were collected on 25th February, and the last collection 

 of a measurable quantity was made on 1 9th April, although a few eggs 

 were netted at intervals until 16th May. In ordinary seasons, when 

 there was a fairly large number of spawning adults in the pond, the first 

 collections of eggs were obtained usually in the latter part of January 

 and the last in the early part of May, the dates varying a little owing 

 to the temperature and other circumstances. The total number of eggs 

 obtained from the pond in 1907 was estimated at about 1,626,000, 

 whereas in 1906 — when the supply of adult plaice was also much below 

 what is necessary — the number was 7,486,000. Of the total, about 

 40,000 were collected in February, 1,213,000 in March, and 373,000 in 

 April ; the largest number were obtained between 16th and 26th 

 March, when about 660,000 were collected. The estimated number of 

 dead eggs which were removed from the hatching apparatus during the 

 season was 345,000, showing a death rate of about 21 per cent., or 

 about half of what it was in the previous year, when the filtering and 

 water supply arrangements were defective. Included in the measure- 

 ments of dead eggs are the shells of those which hatched out, so that 

 the number is in reality less than that stated. The estimated number 

 of fry of plaice which were "planted" in the sea was 1,282,000. They 

 were all liberated in the neighbourhood of the hatchery, mostly on 1st 

 April, 12th April, and 25th April, in from 10| to 11| fathoms, the 

 surface temperature ranging from 42*8 to 43*5 F. 



The fishermen of the northern part of the coast of Aberdeenshire 

 requested that plaice fry from the hatchery should be liberated in their 

 localities as in some former seasons, but owing to the small numbers that 

 were at any one time available it was not thought desirable to incur the 

 expense required in doing so. 



During the season there were considerable fluctuations in the 

 temperature of the water in the spawning pond, as may be seen from 

 the table appended. On the 30th December the temperature fell to 

 29*5 F., and on the next day it was still lower, viz., 29*1 F. In the 

 early part of January it rose, reaching 41 and 42 F. in the period from 

 12th to 16th, but later in the month and in the first part of February it 

 was very low, falling to 31*3 F. on 6th February and being under 33'4 F. 

 from the 26th January to February 11th. The frost was so severe in 

 the first days of February that the supply of sea water to the tank- 

 house was frozen up. The temperature of the water in the pond fell 



G 



