494 REPORT OF THE COUNCIL. 



following table shows the numbers of fish of various species dealt 

 with : — 



From a first examination of the results the following table has been 

 drawn up, showing approximately for the various species the sizes at 

 which 50 per cent of the fish are retained in the cod-end : — 



Otter Tkawl. Beam Trawl. 

 Plaice — 10-5 cm. 



Dabs 14 cm. 12 cm. 



Haddock 19 cm. — 



Whiting 19-20 cm. 14-5 cm. 

 Cod ca. 20 cm. ca. 14 cm. 



It will be seen that the beam trawl, which has a smaller mesh than 

 has the otter, retains a larger percentage of the smaller fish. 



Marking Experiments. — The plaice-marking experiments of the 

 years 1906-8 are under examination. The results of these experiments 

 confirm conclusions drawn from previous experiments made in the 

 Southern Bight and on the Eastern G-rounds, and add considerably to 

 the knowledge of the movements of plaice on the Flamborough Off and 

 adjacent grounds. 



Invertebrate Fauna. — The report on the Invertebrate Fauna is 

 approaching completion. The records have been classified in grounds 

 whose delimitation has been carried out with reference primarily to 

 the texture of the bottom, with, in the case of the larger grounds, 

 subdivisions based on depth or average salinity, or made by arbitrary 

 lines. 



A study has also been made of the frequency of capture of the 

 various species in tlie grounds chosen, and of the comparative im- 

 portance of depth and texture in determining distribution in the North 

 Sea. 



Bottom Deposits. — A report on the bottom deposits is approaching 

 completion. It is based on the examination of 568 samples, together 

 with records obtained from material brought up in trawling and 

 dredging. The distribution of various grades of deposit has been 



