168 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ON THE PLAICE MEASUKEMENTS MADE IN THE 

 EASTERN WATEES OF THE IRISH SEA 

 DURING THE YEAES 1909-1913. 



By Jas. Johnstone, D.Sc. 



Contents. 



1. Introduction 168 



2. The statistical methods employed 170 



3. Distribution and migrations of plaice on the fishing grounds 182 



(a) Nelson Buoy to Liverpool Bar 182 



(6) Mersey shrimping grounds 189 



(c) The Horse Channel grounds 191 



(d) The plaice-fishery in Beaumaris and Red Wharf Bays 193 



(e) The Luce Bay plaice-fishery 200 



4. Growth and age-groups 202 



5. Distribution of the age-groups on the fishing grounds 210 



6. The question of size-limits 212 



7. The length-weight coefficient, &c [ 214 



(1) Introduction. 



The abstracts of the measurements made at sea and 

 in the laboratory during the year 1913 are presented here 

 in continuation of former reports, but an attempt has 

 also been made to summarise all the data collected during 

 the period 1909-1913. This series of investigations was 

 initiated in 1908, with the object of providing material for 

 a discussion of the question of which particular trawl- 

 mesh might be generally allowed in the Lancashire and 

 Western Sea Fisheries District, and with the adoption 

 of a six-inch mesh for use inside the district the 

 immediate object of the investigations was attained. In 

 1910, however, the scheme of work previously followed 

 was amplified, and was adopted in 1911, when assistance 

 from the Development Fund was obtained by the Com- 

 mittee. It was hoped that the amplified scheme would 



