38 Fishery Board for Scotland. 



months. Further, these figures show by the absence of plaice eggs in 

 February, and the presence of a large percentage of eggs in the later 

 stages of development, that the inner Firth of Forth derives some of its 

 plaice stock from areas nearer the open sea. 



Professor Thompson tells us that Carnoustie and St. Andrews 

 represent a characteristic region, where a younger class of fish resides ; 

 at the Firth of Forth Stations we have older fish, not markedly segre- 

 gated on this or that station according to age, but with a greater and 

 greater admixture of older fish as we pass to the outward and deeper 

 waters. 



" Again, the middle half (or 50 per cent, zone) of the plaice in the 

 shallower estuarine bays is a quite separate lot of fish, not overlapping 

 but wholly inferior in size (and age) to the similar middle block of the 

 fish in the deeper waters at the mouth of the Firth of Forth. 



" Further, in all the Firth of Forth Stations except one (Station IV.) 

 the lower decile is over 25 cms. ; in other words, that well over 90 per 

 cent, of the fish caught are above the size which it has been proposed to 

 protect by a legalised ' size-limit.' 



" In regard to the seasonal distribution of plaice in the Firth of 

 Forth," he says " that if we examine the mean of all the stations, we 

 see that the maximum catches are between July and September, and 

 that the smallest catches, only one-fourth or one-fifth as great, are 

 from January to March. At all stations the maximum lies either in the 

 second or third quarter of the year, and in most cases in the third. It 

 occurs in the second, or April-June quarter in the case of Stations II, 

 IV., and VII. ; and these are the three shallow- water stations, in the 

 bays on the north and south sides of the Firth. The season of minimum 

 is not quite so regular, and, on these stations where the catch is small, 

 is not so well defined ; but usually (on Stations I., II., V., VI., VII., 

 and IX.) it falls in the first quarter of the year." 



I have quoted these statements because, taken together with these 

 records of the distribution of the eggs of plaice, they epitomise the life- 

 history of this species in the Firth of Forth very succinctly. 



Plaice spawn at the outer reaches of the estuary especially in the 

 neighbourhood of the Fife Coast and east of the May Island. Some 

 years are more favourable for spawning than others. Spawning begins 

 somewhat ear her to the east of the May Island than on the Fife Coast. 

 Those localities are only relatively of importance when compared with 

 neighbouring localities, and fall very far short of such an area as that 

 of the Dornoch Firth. Pelagic plaice eggs are always rare over the 

 inner and shallower waters of the Firth of Forth, and eggs in the later 

 stages of development appear in the plankton as early as the newly 

 spawned eggs. Thus only sporadic plaice appear to spawn in the 

 inner waters of the estuary, although plaice eggs may be derived from 

 the outer area. 



The percentage of very small plaice in the Firth of Forth is very 

 small even at the inner and shallower stations. Accordingly only a 

 very small stock of the 0-group of plaice can be added yearly from 

 eggs spawned outside the Firth. There is no evidence at present as to 

 whether the stock of plaice belonging to the older age groups within 

 the Firth are derived entirely from this 0-group, or whether the stock 

 is augmented by the immigration of immature plaice from the outer 

 areas. Extremely few plaice of adult size are found in the inner waters 



