426 REI'OKT OF THE COUNCIL. 



growth is continuous between the Dogger Bank and the coastal grounds 

 north of Flamborough Head. 



Other experiments have also been devised, and are being carried 

 out to test whether the still smaller year-old fish of a length of two 

 to four inches can be profitably transplanted to these depleted waters. 



Special Experiments. — The special investigations enumerated in 

 the last annual report have been continued. Further reference to the 

 more extensive of these experiments is made in the next section. 



B. LABOEATOliY INVESTIGATIONS. 



Age of Fishes. — The material which has been accumulated for 

 studying the age of plaice at different sizes on the various fishing 

 grounds consists of more than 12,000 otolitlis, of which nearly 8000 

 have been collected from measured fish caught on board the Huxley 

 during the past year. 



Much time has been spent upon the study of this material, and a 

 report upon the data acquired up to the end of 1905 is now in prepara- 

 tion. The results attained by this method have been of great value in 

 throwing light upon the distribution of the various age-groups of 

 plaice, the rate of growth in different regions, the age of the two sexes 

 at first maturity, and similar problems. 



In consequence of the relation which has been found to exist between 

 depth and distance from shore on the one hand and the size of plaice at 

 a given age on the other, and in view of the irregular character of the 

 ground off the English coast, a continuous series of hauls of the trawl 

 was carried out in May, 1905, on a line from the Leman Ground to the 

 Dutch coast (which represents apparently the main axis of the off-shore 

 migrations of plaice in the southern part of the North Sea), and the 

 otoliths of all the plaice caught were extracted. 



This experiment was repeated in September last, and again in May 

 of the current year, the collections yielding from 2000 to 3000 otoliths 

 on each occasion. 



The results of these experiments have furnished a standard by 

 which to estimate the value of results obtained from samples in isolated 

 localities. 



Food of Fishes. — The material collected bearing upon this point 

 amounts now to about 10,000 stomachs of fish, the contents of which 

 have been systematically recorded. During the past year the food of 



