xviii 



Thirty-fourth Annual Report 



minute floating organisms, on which the herring mainly subsists. At 

 a number of places in the Loch, a series of temperature observations 

 are made at different levels, and collections of the floating food secured, 

 and it is proposed to continue these investigations until the herrings 

 return to the Loch in their former abundance, so that comparison may 

 be instituted between the observations taken in the period of scarcity 

 and those taken in the period of abundance. 



Fishery Investigations in the North Sea. 



T raiding Investigations. 



The staff have been kept busily engaged in working at the collec- 

 tions of various kinds which were obtained in previous years, and also 

 in dealing with the records of the observations and the statistics 

 obtained. Among these, the following may be mentioned. 



Migration and Growth of Fishes. 



Marking experiments on the plaice were commenced in 1904, and 

 continued until the end of 1913, during which period 8354 plaice were 

 marked and liberated at various stations in the North Sea. Of the 

 total, 4070, or 48*7 per cent., were recaptured up to April 1916. The 

 particulars for each year are shown in the accompanying table : — 



Year of 



Number 



Number 



Percentage 



Liberation. 



Liberated. 



Recaptured. 



Recaptured. 



1904 . 



310 



101 



32-6 



1905 . 



245 



89 



36-4 



1906 . 



40 



12 



(30-0) 



1907 . 



13 



6 



(46-1) 



1908 . 



259 



67 



25-9 



1909 . 



336 



65 



193 



1910 . 



. 1896 



1001 



52-8 



1911 . 



. 1736 



895 



51-6 



1912 . 



. 2175 



1199 



55-1 



1913 . 



. 1344 



635 



47-2 





8354 



4070 



48-7 



A detailed Report on the results of the marking experiments in 

 the years 1904-1909 has already been published, and another Report 

 dealing with the later experiments is now all but completed. A large 

 number of charts have been prepared, showing the course taken by the 

 marked fish liberated at each station, and it is hoped that some at 

 least of the more important of these may be published with the Report. 



Other Investigations. 



Other investigations on which the scientific staff have been engaged, 

 and in regard to which Reports are in course of preparation, include 

 the following : — The influence of herring-trawling on the fish supply ; 

 the life of the herring in captivity ; the determination of the age and 



