364 THE FLOUNDER FAMILY. 



approaching maturity : those from the Frith of Forth apparently 

 chiefly by the channel between the Isle of May and the coast of 

 Fife, and those from St Andrews Bay, reinforced to some extent 

 by those from the Frith, probably moving out from the neighbour- 

 hood of the mouth of the Tay in the direction of the Bell Rock." 



For what reason plaice set free near the south shore of the 

 Frith of Forth should invariably migrate slowly but surely 

 westwards, whilst others set free under similar circumstances 

 on the north shore, should with equal precision travel eastwards 

 round the Carr, across the sandy Bay of St Andrews and on 

 northwards, we cannot possibly say. The problem is as difficult 

 of solution as many another connected with animal migrations. 

 It is possible that a migration such as this, occurring amongst 

 the plaice of Danish waters, may account for the peculiar 

 distribution of this fish, as given by Petersen. 



Plaice appear to have very definite spawning-grounds, 

 always well offshore. Taking the east coast of Scotland as an 

 instance, in the Moray Frith district, 16 miles to seaward and 

 in 20 fathoms of water is situated Smith Bank, at which 

 immense numbers of large spawning plaice are found at the 

 breeding-season, but it has yet to be proved that they do not 

 occur there at other periods of the year. The same spot, which 

 is rich in invertebrate life, is frequented by shoals of cod and 

 haddock and at such a time the surface- and mid-waters contain 

 vast numbers of the eggs of these species. 



In the districts to the south of this, viz., about Montrose, 

 the spawning plaice occur outwards so far as 25 miles offshore, 

 but a little further south, off St Andrews Bay and the 

 Frith of Forth, the spawning adults are again found rather 

 nearer inshore : in the stations just outside the Frith of Forth 

 are found great quantities of eggs of plaice in March and April, 

 mingled with those of the haddock. 



The position of these spawning-areas is doubtless determined 

 by several factors, the exact bearing of each of which we are 

 not yet in a position to appreciate, except that the tendencies 

 of all the movements of the growing plaice bring them to the 

 regions referred to. Dr Fulton 1 gives the results of experiments 



1 S. F. B. Report, 1895, p. 153. 



