14 



Fishery Board for Scotland. 



Sea, and that here the earliest records of the occurrence and the greatest 

 frequency of plaice eggs in the plankton were found. The details of 

 the investigations made in this locality are given very fully in the ac- 

 companying table (p. 13). The table proves that the spawning season 

 begins before the first days in January, and that in exceptionally early 

 seasons it may begin a month earlier. Spawning is very general 

 towards the end of January, and the maximum frequency obtained at 

 any time within this area was reached on 11th January 1908 when 1832 

 eggs were taken in a surface haul of one half-hour's duration. 



As has been stated, in the Northern North Sea the plaice is the 

 species with pelagic eggs in which the reproductive organs in the adult 

 first indicate the approach of the spawning season. It is also the 

 species which spawns first in the Dornoch Firth, and the eggs of the 

 plaice are the only pelagic ones which have been collected as early as 

 December. In the month of January in the Dornoch Firth they 

 constitute on the average over 95 per cent, of the total catch of pelagic 

 eggs, while in February the percentages of plaice eggs in the total 

 catches throughout the ten years ranged from 4 to 78. Other species 

 with pelagic eggs begin to spawn in the locality in February, but with 

 varying intensity from year to year in relation to the plaice. 



The complete table for the Dornoch Firth area is complex because 

 the material from the stations are not strictly comparable from year 

 to year, and indeed only in one particular spawning season, namely, 

 1904-1905, are there records for each month. 



The table of the averaged results for each month gives the best 

 general idea of the conditions within the area. 



Dornoch Firth — Plaice Eggs, 

 averaged results. 



The greatest frequency occurs in January, and there is an orderly 

 decline in February and March. Although there is a decrease in the 

 relative abundance of eggs in the initial stages of development the 

 absolute number obtained even in March is high. The Dornoch Firth 

 is therefore a real spawning area from December to March, but the 

 intensity of spawning which is greatest in January falls off in the 

 succeeding months. It is problematical, however, whether the increase 

 ill the relative abundance of the eggs in the later stages of development 

 in February and March is altogether due to the presence of eggs which 



