— 85 — ■ COUNCIL-MARCH 1920- APPENDIX 



in relation to the other class in the second period [1906 — 1910] compared with 

 the first [1901 — 1905] the small plaice have increased in proportion in each of 

 them, that which has taken place in square XXIII., off the coast of Aberdeenshire 

 being especially noteworthy. 



The statistics above discussed show that the plaice as a species has diminished 

 in abundance, or at all events in weight landed per unit of fishing, during the ten 

 years over which the statistics extend [1901 — 1910], and this conclusion is in agree- 

 ment with the opinions so often and strongly expressed by the practical men". 



Dr. Masterman, in his aforesaid paper, deals especially with English Plaice- 

 Statistics for the years 1906 — 1912. He arrives here at the following results (1. c. 

 p. 114): 



"In the whole catch for the North Sea there is a reduction of the proportion 

 of large plaice from 36.0 per cent, to 19.0 per cent., an increase of medium plaice 

 from 25.0 per cent, to 32.6 per cent., and an increase in relative proportion of small 

 plaice from 31.5 per cent, to 41.5 per cent. These summary figures are of limited 

 application, and an analysis into areas and methods of capture has shown that the 

 increase in small plaice on the grounds, both relative and absolute, is much greater 

 than this, as the figures are affected by an abandonment of fishing in recent years in 

 the chief nursery areas. In any case, it is evident that there has been since 1906 a 

 large increase, both relatively to total catch of plaice and absolutely, in the catch of 

 small plaice in the North Sea, and a large decrease in that of large plaice. 



As to the causes of this phenomenon, there can be little doubt that the latter 

 is due to excessive fishing by man. In other words, the destruction by man is of 

 sufficient intensity to reduce materially the probabiHty of fife of the plaice in the 

 North Sea; this is shown in the greatest degree on the southern grounds where the 

 intensity of fishing is greatest. Whether it can be regarded as in any degree a mis- 

 fortune or as endangering the future supply of plaice is a question that need not 

 be discussed here". 



It will be seen that Dr. Masterman's results confirm the results of Prof. 

 Heincke, as far as the large plaice are concerned. The increase in relative proportion 

 of medium plaice, which Masterman has noticed in the period 1906 — 1912, is a very 

 noteworthy phenomenon, but it must be remembered, firstly, that an evidence of 

 this kind among a great series of observations from various countries stands very 

 isolated, secondly — (what Masterman himself regards as a possibility) — that "the 

 increase in small and medium plaice may be a natural phenomenon of the same 

 nature as the yearly fluctuations which it has been suggested are due to variations 

 in the abundance of each year-brood. Certain very favourable physical conditions 

 may conduce to the production of a large brood of fish in any one year, and behind 

 the fluctuations in these conditions there may be some general cyclic change in 

 physical conditions which may have an amplitude of several years. The period of 



