5 - 



LATER STAGES: PLKWHONECTIDS 



even upon the occurrence of certain kinds of fish. Without a more detailed analysis of 

 the commercial ligures, all hypotheses are mere conjecture. In any case, the seasonal 

 fluctuations and the consequent variation in the standard of "one day's absence" are shown 

 to be of a very small character unlikely to seriously affect any conclusions as to seasonal 

 changes in distribution of fish derived from statistics of the average monthly catch per day. 



Appendix Tables 3 

 — 12 give the monthly 

 catch in kilos per day 

 of each of the species of 

 pleuronectid here dealt 

 with, and the figures are 

 illustrated graphically 

 in the accompanying 

 diagrams. (Figs. 1 — 7). 

 It is possible by a 

 study to obtain cer- 

 tain indications of regu- 

 larly occurring seasonal 

 changes. 



In the case of soles, 

 (Fig. 1 and App. Table 

 3) the greatest catches 

 indicating the closest 

 density of fish, are found 

 in the two shallow water 

 inshore areas A z and A,. 

 To a large extent there 

 is an inverse relation 

 between these areas on 

 the one hand and the 

 deeper water areas on 

 the other. In the A areas 

 the greater intensity of 

 catch is found in May 

 or June, with spring and 

 autumn minima. In the 

 case of Ai which is off the 

 south-east coast of Eng- 

 land (records for steam 

 trawlers are principally 



from the Wash district) the spring minimum and the summer maximum are both a month 

 earlier than in A 3 (off the Danish Coast). The actual catch per day in A t is roughly about 

 double that in A 3 throughout the year. The curve for B 4 partakes rather of the character of 

 its inshore neighbour, A.. It has the same spring minimum, June maximum and September mini- 

 mum but there is a less degree of variation and the maximum does not go above 20 kilos per 



Figure i. Average catch of Soles per day by Steam Trawlers, in certain areas 

 of the North Sea. (Mean of the 4 years 1906 — 1909). 



Soles. 



