REPORT OF THE COUNCIL. 401 



(ii) Experiments on the proportion of small fishes vvhicli escape 

 through the meshes of the commercial trawl. 



(iii) Investigations on the rough grounds unsuitable for commercial 

 trawling. 



(iv) Collection of samples of bottom deposits. 



(v) Experiments on bottom currents by means of Mr. Bidder's drift- 

 bottles. 



(vi) Collection of fish-stomachs, for determining the food of fishes. 



(vii) Collection of otoliths from trawled fish for investigations on 

 the age of fishes at diherent sizes. 



B. LABORATOEY INVESTIGATIONS. 



Age of Fishes. — Considerable progress has been made with the 

 otolith investigations. The growth-rate of the Plaice during the first 

 few years of its life has been definitely determined for several different 

 parts of the coast. The results show a substantial agreement over the 

 southern part of the North Sea, but a much more rapid growth in the 

 western part of the English Channel than in the former area. The 

 determination of the relation between age and size during the later 

 years is beset with difficulties connected with the existence of local 

 differences of growth on the offshore grounds, complicated by the 

 migrations of the fish. These points are being carefully investigated. 

 The method of study has been extended during the year to other 

 suitable species, especially the Cod. 



Food of Fishes.— Records of the general fauna of the different 

 trawling grounds have been kept systematically, and have been 

 supplemented from time to time by the results of special hauls with 

 the dredge and other implements. 



The contents of over 6,000 stomachs of fishes have been examined 

 and recorded in detail. 



The age and food of all marked fishes recaptured has been regularly 

 recorded. 



Bottom Deposits. — Samples of the sea-bottom from about 200 

 localities have been collected from time to time, and are under analysis 

 with the object of determining the influence of this factor on the 

 distribution of fishes and of the organisms upon which they feed. 



C. FISHERMEN'S RECORDS. 

 The system of fishermen's trawling records has been continued 

 without interruption. Thrive or four Lowestoft and Ramsgate smacks, 



