SEA-FISHERIES LABORATORY. 



101 



THE PLAICE FISHERIES OF THE IRISH SEA 



BY 



JAS. JOHNSTONE, D.Sc. ; W. BIRTWISTLE 

 and W. C. SMITH 



CONTENTS 

 PART I : The Pre-War Period, 1908-1913 



Introduction 



The area investigated, p. 104 ; Nature and regulation of the 

 grounds, 106 ; Distribution of the various species of fish, p. 109; 

 Tables I and II, species of fish found, p. 110 ; Seasonal fisheries, 

 p. 113 ; Migratory fishes, p. 114 ; Long period fluctuations in 

 the fisheries, p. 116. 



Methods of investigation 



Treatment of the data 



Statistical methods, p. 120; Pearson curves, p. 122; Summational 

 curves, p. 124 ; Use of the same, p. 129 ; Measures of dispersion, 

 p. 131. 



Lengths of the plaice caught 



Tables III to XIII, Length frequencies on the grounds during 

 1908-1913, p. 137 . Prevalent lengths, 149. 



PAGE 



103 

 103 



117 



119 



135 



PART II : The Life-History of the Plaice 



The spawning grounds 



The hatching and transformation stages 



The first shore stages 



Food of the larvae and transformed plaice 

 Growth of the plaice during the first year 

 The nursery grounds and their conditions 



The rate of growth of the plaice 



Tables XIV and XV, length frequencies 

 p. 168 ; Ratio of males to females, p 

 maturity, p. 172. 



for age-groups O-IV, 

 171 ; Sizes at sexual 



152 

 152 

 157 

 158 

 159 

 160 

 163 

 166 



