Distribution of Plaice Eggs — Moray Firth. 



19 



Plaice eggs were more uniformly distributed throughout the 

 different water layers in 1905 than in 1908, for if the hauls from the 

 deeper layers are to be taken as representing not only horizontal but 

 also vertical hauls these must be taken for both series of experiments. 

 The uniformity of the distribution of plaice eggs throughout the different 

 water layers in 1905 is also well illustrated in the numbers taken in the 

 Petersen Youns Fish Trawl at the same station. 



Petekson Young Fish Trawl. — Station 30. — 

 26th January 1905. 



Stage of Development. a 



Surface Haul — one half-hour 1 

 Mid-water Haul — one half-hour 2 

 Bottom Haul — one half-hour 2 



Although the numbers are small they are significant. In 1908, when the 

 eggs were just recently spawned, they were all at the surface ; on the 

 other hand, in 1905, when many of the eggs were far advanced in de- 

 velopment, they are more equally distributed throughout the different 

 water layers. 



The number of eggs at the " a " stage of development obtained in 

 January 1908 shows that plaice spawn as far as thirty miles eastward of 

 Dornoch Firth. 



For the month of February there are no fewer than seven separate 

 observations showing considerable variation from year to year. In 

 1909 and 1911 no plaice eggs were taken in the surface nets, but on the 

 7th of February 1907 as many as 112 were obtained in a haul of one 

 half-houi's duration, and 64 of these were newly spawned. On this 

 date plaice eggs constituted 99 per cent, of the total eggs captured. 

 The averaged results for this month are as follows : — 



With the exception of the year 1907, there was always a greater 

 percentage of eggs in the later stages of development than was found 

 in the Dornoch Firth or at Station 29 at the corresponding date. 

 Although plaice spawn here in smaller numbers than nearer the shore, 

 there is always in this month a relatively gi'eater percentage of eggs 

 in the later stages of development, and these have had their origin 

 outside the locality. 



This station was visited on 31st March 1905, and again on 7th March 

 1911, and the frequency of plaice eggs at the surface was eight on both 

 occasions. In 1905, however, four of these even on the last day of the 

 month were newly spawned, while in 1911, early in March, all the eggs 



