— 69 — 



lower than that during 1920 in the North Sea, notwithstanding a decrease in total 

 trawhng in the later year. 



A considerable amount of work has been carried out with the Petersen 

 bottom sampler, principally in a selected area on the Dogger Bank with a view 

 primarily to finding out the amount of plaice food present. In 1921 this area was 

 sampled on three occasions in August, September and November, a total of 200 

 stations being worked. The results, especially with the larger 0.2 m^ grab, have 

 been encouraging, and will be of great importance should transplantation of plaice 

 be carried out in the future. The stomachs of plaice taken in the area have been 

 examined. Hauls were made in 1921 in other localities to the number of 67. 



In 1922 intensive work was continued on the Dogger and in the vicinity 

 of the Haaks Light vessel, these grounds being typical plaice grounds of varying 

 character. The Petersen grab was used at carefully arranged stations one mile 

 apart, with numbered 189 and 58 respectively on the two grounds mentioned. 

 The work was interrupted by loss of gear: it is intended to extend it to the Leman 

 Ground. 



In addition, further stations were worked on the Dogger with a view to 

 delimiting a patch of Spisula siibtruncata. The patch proved to have an area of 

 at least 38 square miles, with an average of 375 and a maximum of 3000 individuals 

 per square meter. 



The results will, it is hoped, contribute towards determining the intensity 

 of work with the grab necessary adequately to sample the ground. 



A report by Dr. Blegvad, Assistant at the Danish Biological Station, on 

 the results of the bottom sampling cruise carried out by the "George Bligh" from 

 Lowestoft to Esbjerg in July 1921, has been published by the Zoological Society 

 of London (Proc. Zool. Soc. 1922, pp. 27—32). 



Scotland. In Scotland, investigations on the same lines as those carried 

 out in previous years have been continued, this course being considered advisable 

 owing to the adoption of the seine-net by Scottish fishermen. 



During the year 1st July 1921 to 30th June 1922, the Moray Firth was 

 visited five times and the grounds off the Aberdeenshire coast were surveyed on 

 four occasions by the research vessel. All plaice captured were measured. Otoliths 

 were extracted from approximately 4.400 fish taken in the first mentioned area 

 and more than half of these have been examined. The second area yielded nearly 

 1.800 otoliths, the examination of which has been completed. From the data pro- 

 cured there seems to be a marked difference in the rate of growth of the younger 

 fish from the two areas. The average sizes of the lower age-groups of the Moray 

 Firth fish appear to be considerably less than those of the fish caught off the Aber- 

 deenshire coast. 



Over 2.000 very small plaice (1.800 below 14 cm) were caught in the course 



