12 Fishery Board for Scotland. 



single haul. This rich haul is closely followed by one from Lossiemouth, 

 where 1294 eggs were captured on 22nd March 1906 in a similar haul of 

 like duration. These two hauls are easily the richest for the whole 

 period considered. The frequencies of several of the stations within 

 the Moray Firth area come next, though a very long way behind. 

 Outside the Moray Firth the figures are very poor, the only frequency 

 over one hundred being obtained at Bressay (near Lerwick). At 

 Tod Head, on the East of Scotland, 82 plaice eggs were obtained in 

 the surface net in one half-hour — a result which compares very un- 

 favourably with the richer Moray Firth grounds. But still poorer 

 are the results got from the area immediately outside the Firth of Forth. 

 Unfortunately, no observations were made in the region between this 

 area and the Northumberland coast, otherwise they would help to 

 link up the Scottish records with those from the Southern North Sea. 



The general conclusions, as deduced from these tables are, (1) that 

 the Northern North Sea is a spawning area of minor importance for 

 plaice when compared with the Southern North Sea, and 



(2) that within the Northern North Sea area the Moray Firth is 

 by far the most favoured locality for plaice during the spawning season. 



The method of tabvilation just described gives only the com- 

 parative frequencies of plaice eggs within the different areas. An 

 area of low frequency, however, may possibly be a spawning area, 

 although the total number of individuals spawning within the area may 

 be very small in comparison to the numbers found in the areas of highest 

 frequency. Such low frequency might be due to the intensity of fishing 

 within the area. The percentages of plaice eggs in the different stages 

 of development at those localities where more than twenty eggs have 

 been captured has been taken as a standard of comparison. Pelagic eggs 

 in the initial stages of development belong to the near neighbourhood 

 in which they are fished. On the other hand, eggs in the later stages of 

 development may be of composite origin. They may have drifted 

 from some considerable distance into the area in which they are fished, 

 or they may have been spawned within the area some time previously. 

 It is just for this reason that observations made early in the spawning 

 season are of such vital importance in the determination of spawning 

 grounds. Any table that can at present be made embodying the facts 

 cannot be completely representative until all areas have been fre- 

 quently investigated in the early months of spawning. At the one ex- 

 treme of such a table there are those localities at which more than 

 80 per cent, of the eggs were in the initial stages of development, at the 

 other extreme where all the eggs were in the later stages of development. 

 The positions at which more than 80 per cent, of the eggs were newly 

 spawned correspond very closely with the localities of gxeatest 

 frequency. As the eggs -advance in development there is a marked 

 expansion in the area of distribution — a result which might have been 

 anticipated. It seems as if the plaice spawn in comparatively restricted 

 areas and the positions of the stations where the eggs occur with 

 greatest frequency, and where the percentage of eggs in the " a " stage 

 of development is high are all very near the coast well within the thirty 

 fathom line. At Noss Head (Caithness) and Station 26 (58° 11' N. ; 

 0° 32' W.) the depth is, however, over thirty fathoms. Noss Head 

 Station is only three miles from the rapidly shelving coastline, whilst 

 Station 26 is in the vicinity of a small shallow bank in the Moray Firth. 



