SEA-FISHERIES LABORATORY. 



209 



we are comparing a definite period (August-September) in all 

 the years, and it may be the case that large plaice had left 

 Liverpool Bay, in greater proportion, and in a certain month, 

 in one year than in another. 



Fig 18. Graph representing the lengths of plaice caught by the 6-inch 

 trawl-net on the Liverpool Bay grounds in the months August-September 

 during the period 1909-13, 1920. Summational curves, from Tables 5, 23, 24. 



The Northern Plaice Grounds in 1920 and 1921. 



There is material for an interesting comparison in the 

 data obtained on the northern grounds in 1920-1921, when 

 investigations into the spawning of the fish were made, and 

 when we were able (by permission of the Fishery Board for 

 Scotland) to trawl in Luce Bay. The Table 17 gives the 

 length-frequencies tor the months of January to April, and for 

 the " Shoals " and " Slaughter " grounds (the latter being that 

 on which spawning fish were found). Fig. 19 is a graph of these 

 data, and also the results of the hauls made in Luce Bay in 

 1920-21. 



