CONSIDERATION OF INDIVIDUAL FISH 85 



The period of thirteen years over which these experiments have 

 extended is a considerable one, and Dr. Fulton thinks it is reasonable 

 to believe that the greatly increased average abundance of the 

 young plaice in the first years was mainly due to the liberation of 

 the fry from the hatchery ; and that, on the other hand, the decrease 

 in the abundance in the last six years was mainly owing to the fact 

 that no plaice fry were added to the loch in those years. 



The transplantation of young plaice from one ground to another 

 has been suggested as a means of increasing the yield of the plaice 

 fisheries of the North Sea. The question was discussed at a Con- 

 ference of representatives of the sea fishing industries of the United 

 Kingdom, convened by the National Sea Fisheries Protection 

 Association at Grimsby in 1902, and again at a subsequent Con- 

 ference held at Aberdeen in 1905. Apparently the idea of trans- 

 planting young plaice to a suitable feeding ground originated in 

 Denmark, where certain experiments were carried out by Petersen, ^ 

 who transplanted young plaice from the North Sea to an inland 

 lagoon known as the Thisted Bredning. Fish so transplanted were 

 reported to have increased in growth in a remarkable manner. 



In the North Sea experiments on the transplantation of small 

 plaice from shallow inshore grounds to the richer feeding ground of 

 the Dogger Bank, were first carried out by the Marine Biological 

 Association in 1904. The rapid growth of the fish thus transplanted, 

 when compared with the growth of fish of similar sizes remaining 

 on the inshore grounds, was described by Garstang* in one of the 

 earlier reports on the North Sea investigations of the Marine 

 Biological Association. Similar experiments were carried out sub- 

 sequently in each year up to and including 1908, and the results are 

 summarised in an elaborate memoir by Borley.* The rapid growth 

 of the plaice transplanted to the Dogger Bank was repeated in each 

 year, and although its amount varied slightly the whole series of 

 experiments places the reality of the increased growth beyond 

 reasonable doubt. 



If the results of all the Dogger Bank experiments for the years 

 1904-8 are combined, the average growth in length of the plaice 

 recaptured one year after liberation is Sj in., the average initial 

 size of the fish transplanted being about 8f in. The fish have thus 

 grown from an average size of 8| in. to an average size of 14 in. in 

 one year. Had they remained on the inshore grounds from which 

 they were taken the annual growth would have been only 2 in. 



1 Reports from the Danish Biological Station, VI, Copenhagen, 1896. 



' " Experiments in the transplantation of small plaice to the Dogger Bank. 

 International Investigations," M.B.A. Report, I. (Cd. 2670, 1905.) 



» " Report on the experimental transplantation of plaice to the Dogger Ban.k 

 International Investigations," M.B.A . Report, IV. Southern Area. (Cd. 6125, 1912.) 



