REPORT OF THE COUNCIL. 495 



studied, and a provisional division of the southern part of the North 

 Sea into grounds on the basis of the textures of tlie bottom carried 

 out. 



Bottom Trailer Experiments. — The particulars obtained from the 

 cards returned from Mr. Bidder's Bottom Trailer experiments have 

 been arranged and analysed. Three new series of experiments conducted 

 in 1906 have been examined, and three old series of 1904 and 1905 

 revised. The direction of the bottom currents and the approximate 

 velocities have been ascertained. The series are mutually confirmatory 

 in their indications. A very large number of the bottles have been 

 recovered, 81 per cent of the cards from the first series having been 

 returned. The percentage returned within twelve months of their 

 being put out is between 50 and 60 per cent. 



C. FISHERMEN'S EECORDS. 



A report on the Lowestoft Trawling Records, dealing with plaice and 

 soles, has been completed and published. 



A report on the catches of plaice, soles, turbot, and brill by the 

 Grimsby trawlers is approaching completion. The monthly average 

 catches in different areas have been calculated and analysed. The 

 report deals with 13,246 hauls, made from 1904 to 1907, during nearly 

 50,000 hours' fishing. 



All these species are found to be relatively very numerous on 

 the Eastern Grounds, off the Danisli coasts, and to decrease rapidly from 

 east to west, and all, with the exception of brill, show fairly regular 

 seasonal variations in several areas. Plaice show an off-shore move- 

 ment from the Eastern Ground in the summer, large plaice appear 

 to migrate southwards in the winter, while small plaice disappear 

 almost entirely from the catches at this time. 



Soles show a very definite distribution. They are limited to the 

 grounds south of a line drawn from tlie Horn Reef North Grounds to 

 the neighbourhood of Flamborough Head. North of this line in the 

 region investigated they are very scarce. 



Turbot and brill have also been examined. 



The records are now beincj examined with regard to the catches of 

 cod, haddock, and whiting, and the monthly averages for the period 

 1904 to 1907 have been calculated for each area. 



The records have yielded material for determining the relation 

 between various statistical units, and factors connecting the rate of 

 fishing per voyage, per day, per haul, and per hour have been 

 calculated. 



