— 15 — LATER STAGES: PLEURONECTIDS 



Plaice. 



The comparative distribution is shown by a chart tinted to represent varying inten- 

 sities. The results confirm those already acquired. Very large amounts are taken from 

 the Eastern areas A 3 B 4 B 5 and B 3) sometimes the mean monthly value for the year being- 

 over 9 cwts. per 10 hours' fishing. There is a great contrast shown on the Western side 

 of the North Sea — from 3-4 cwts. per 10 hours being the amount taken in areas 

 B 2 and B 3 and much less in the deeper grounds C and D. There is a regular sequence 

 of decreasing amount from the German coasts offshore to the Dogger and this ground and 

 all north of it yield mean values for the year of less than 1 cwt. per 10 hours' fishing. 

 Correlated with this change there is shown to be an increasing proportion of "large" fish. 

 "Small" fish predominate almost exclusively on the eastern grounds — "medium" on the 

 intermediate grounds and "large" on the Dogger and on the grounds west and north of it. 



Yearly variations. The changes in the yearly stock are not of the same nature 

 throughout the whole region investigated as complementary fluctuations between the in- 

 shore and offshore grounds can be traced. But, taken as a whole we find in this region 

 a decline between 1904 and 1907. This decline was not always continuous, 1905 being 

 in some cases better than 1904 and 1907 than 1906. The very poor values found in 

 the shallower and most fished areas for 1906, affect the statistics for the whole year and 

 are most striking. They are accompanied by remarkable abundance in the summer of 

 that year, in the grounds north of the Dogger and the suggestion is made that these 

 occurrences may be correlated with the very unusual conditions of temperature and salinity 

 that were a feature of 1906. 



Seasonal fluctuations. On the charts ot distribution are shown, where it has been 

 determined for any area, the period of maximum abundance — a double maximum oc- 

 curs in some areas, notably in areas A 3 B 4 and B 3 and parts of C 2 . As the general rule 

 the coastal grounds have a spring and autumn maximum and the offshore grounds a 

 summer maximum period. Sometimes the summer maximum is sharply defined, as in the 

 outer part of B 3 . Sometimes it extends over a fairly long period as in parts of C 2 . In 

 some of the western areas there are indications of a winter maximum, which is supposed 

 to be connected with the spawning migrations of the plaice. 



One feature which is of interest in these statistics is the change in the size-constitu- 

 tion of the catch during the course of the year. Large fish are in greater proportions in 

 the spring than in the summer and autumn. 



Spawning. The particulars given by the fishermen as to the numbers of plaice 

 spawning or maturing yield but very general results. In all the deep water areas they 

 were to be found maturing during the months of December and January, and actually 

 spawning fish during the months of December to March most of them being in January 

 and February. 



The spawning fish were not present in all the hauls in these months but only in a 

 certain proportion of them. 



Soles. 



One of the chief points in distribution ol soles is the exceedingly rapid diminution in 

 their numbers from the coastal grounds towards the deeper offshore water. Some of the 

 north-eastern areas give no soles at all and on the Dogger Bank and the grounds just 

 to the north the catch is less than one per 10 hours' fishing. On the other hand we 



