of the Fishery Board for Scotland. 337 



southwards to some distance along the English coast." It is noteworthy 

 that the parts of the North Sea in whicli the larger varieties of plaice 

 are obtained, whether on the western or the eastern side, are included 

 within the limits of the North Sea current, as shown by my observa- 

 tions, * while the parts where the smaller varieties are obtained are 

 included in the water which goes northwards from the English Channel, 

 as shown by Garstang.t The plaice on the west coast of Scotland as 

 at Plymoutli, belong to the smaller kind. 



THE PLAICE {Pleuronectes jdatessa, L.). 



The rate of growth of the plaice has been investigated by several 

 naturalists. Mr. J. T. Cunningham in 1891 made a comparison 

 between the sizes of a number of plaice from 3"5 to 31 "5 centimetres, 

 and caught at various times between June 1889 and September 1891, 

 and he provisionally deduced their age. The total number of 

 specimens was, however, small — only seventy-four — and relying on 

 certain experiments in rearing flounders in tanks, which iu some cases 

 showed a very rapid growth, this naturalist overestimated the rapidity 

 of the growth of the plaice under natural conditions. He was of 

 opinion that this species could not reach a size of twelve inches 

 (30'5 cm.) in less than two years, and that it did not begin to breed 

 initil it was two years old, and over eight inches in length, on the south 

 coast of England, where the species is relatively smaller than in the 

 North Sea.} 



Some years later Mr. Cunningham carried on investigations on plaice 

 from vaiious parts of the North Sea, chiefly with reference to the 

 average size when first mature, and expressed a similar view, stating 

 that specimens averaging about thirteen inches in December were 

 scarcely two years old, and that those taken of!" the German and 

 Danish coast in spiing and summer, and langing from seven to ten 

 inches in length, were one year old.§ 



In 1893 I published a paper on the migrations and rate of growth of 

 certain fishes, the data being derived from experiments in marking 

 fish, which were measured and returned to the sea, and were re- 

 measured when captured, i The increase in size was, as a rule, very 

 small, owing to the irritation caused by the attachment of the label to 

 the fish ; but in some cases a considerable increase was found to have 

 taken place. In view of the fact that one plaice, notwith.standing the 

 irritation of the label, increased in length from lOf inches to I3:j 

 inches during the 353 days it was living in the sea — an increase of 

 nearly three inches — and that some others increased by over two 

 inches in periods somewhat longer, although a scar had been caused by 

 the ligature, I concluded that " a plaice of ten or eleven inches in 

 length, living in the sea under natural conditions, grows at least three 

 or four inches longer in the course of a year." 



In the same year Dr. C. G. J. Petersen published a paper dealing 

 with the plaice, among other things with its growth, and he came to 

 the conclusion that this fish generally required three years to become 

 ripe, but might do so in its second year ; that the size at which it first 

 became ripe was subject to considerable individual variation, and that 



*Fiftfenth Annval Report, Part ilL, 334 (1897). 

 t ./own. Mar. lilol. Assoc. 

 X Journal Marine Biol. As-^oc, ii., 99, 1891. 

 § Ibid., iv., 136, 1896. 



II Eleventh Ann. Rep. Fishery Board for Scotland, Part iii., \k 192 (1893). 

 X 



