342 



NATURE 



[June 22, 1916 



THE OVER-FISHING OF JHE NORTH SEA.^ 

 '^r'HE problem of over-fishing of the North Sea 

 -^ was stated in general terms by several 

 committees of inquiry during the latter decades 

 of the last century, and particularly, in regard to 

 the fishes of which the plaice is the type, by the 

 International Council for Fishery Investigations 

 about ten years ago. Since then a large amount 

 of scientific and statistical research has been 

 carried on in this and other European countries 

 with the object of providing data for international 

 schemes of fishery regulation. A series of reports 

 recently published by the English Board of Agri- 

 culture and Fisheries forms what is obviously a 

 very important contribution towards the settle- 

 ment of these very diflficult questions. The series 

 includes three papers on the routine work dealing 

 with the age, growth, and sexual maturity of the 

 North Sea plaice, with the food of the fish in 

 different areas and at different times, and with the 

 distribution of the sexes. These reports have 

 been prepared by Dr. W. Wallace, Mr. R. A. 

 Todd, and Mr. A. E. Hefford. Miss R. M. Lee 

 reviews an extensive series of commercial trawler 

 statistics dealing with plaice, soles, and haddock; 

 and Lieut. H. J. B. Wollaston gives an account of 

 investigations undertaken with the object of de- 

 limiting the positions of plaice-spawning grounds in 

 the North Sea. These two latter papers are distin- 

 guished by much originality of treatment, clear and 

 orderly presentation of the facts elicited, and read- 

 able discussions of the trend of the data. They 

 contain some noteworthy results : interesting cases 

 of high statistical correlation between the density 

 of plaice and haddock on the various fishing 

 grounds of the North Sea, established by Miss 

 Lee ; and details of some novel methods of plank- 

 ton investigation devised by Lieut. Wollaston. 



The main problem is discussed by Dr. A. T. 

 Masterman. Is there evidence of indubitable over- 

 fishing of the North Sea? In its inception the 

 problem was an international one, and it has, to 

 some extent, been treated as such. But the 

 English trawl-fisheries are so predominant as to 

 make it apparent that the statistical data obtained 

 by the Board of Agriculture and Fisheries must 

 form the main mass of material to be considered. 

 The returns of plaice landed at English ports 

 during the period 1906-1912 are therefore those 

 dealt with by Dr. Masterman. Nevertheless the 

 report to the International Fishery Investigations 

 Council prepared by Dr. Heincke, and published 

 in the seventeenth volume of " Rapports et Proces- 

 \'erbaux," should also be seen by readers of the 

 present papers. 



Dr. Masterman 's report is difficult to read be- 

 cause of the great mass of detail considered. The 

 statistics are complicated rather unnecessarily (in 

 the meantime at least) by the rather minute sub- 

 division of the North Sea into statistical areas, 

 nineteen in all. If the areas are considered indi- 

 vidually the fishery statistics of other North Sea 

 nations must be included, and this has not been 



1 Board of Agriculture and Fisheries. Fishery Invest'galion'!. Series II., 

 .Sea Fisheries Vo'. ii., Nos. 1-5; Vol. iii , No«. i-z. (London: H.M. 

 Stationerv Office, 191 5.) 



NO. 2434, VOL. 97] 



attempted — perhaps it is impracticable. Now the 

 period of time covered by the investigations, 1906— 

 191 2, is far too short to enable us to decide 

 whether over-fishing has actually occurred. There 

 are fluctuations during this period, and these 

 "maximal and minimal years" are not the result 

 of statistical "accidents," for they are demon- 

 strated independently by Miss Lee's data. But they I 

 are fluctuations most probably dependent on, or to 1 

 be associated with, meteorological cyclical events, 

 and do not bear on the question of over-fishing. 



Perhaps over-fishing has been demonstrated by 

 Dr. Masterman as the result of the consideration 

 of the "trade-categories." Plaice landed in 

 England are subdivided into "large," "medium," 

 and "small." The variation in the total annual 

 quantities of all plaice landed during 1906-1912 is 

 not significant, but there is a significant decrease 

 in the quantity of "large," and a compensatory 

 increase in the quantity of "small." These 

 variations in the quantities belonging to the 

 various classes may be unreal, for there are 

 apparently no statistical descriptions of the "cate- 

 gories," and it is not impossible that these have 

 not always been the same throughout the period 

 considered. The terms are trade ones, and the 

 classification is a trade convention made inde- 

 pendently of the system of statistical collection. 

 Nevertheless it is most probably true that modern 

 trawl-fishing has diminished the stock of large 

 plaice inhabiting the North Sea : Dr. Masterman's 

 discussion indicates so much. The composition of 

 a natural fish-population inhabiting this very ex- 

 tensive area has been affected by artificial means. 

 In other words, the " mean after-lifetime " of a 

 plaice inhabiting the North Sea, at the time when 

 it is big enough to be caught in a trawl-net, has 

 been reduced as a result of the development of 

 the British steam-fishing fleets. 



The problem is thus one of the eliciting of facts 

 rather than of the provision of remedial legislative 

 measures. It is highly unlikely that such will be 

 attempted for some time to come, but the thing to 

 be immediately considered is the recommendation 

 made to the various Governments, in 1913, by the 

 International Fishery Investigation Council. This 

 suggested a minimum size-limit upon plaice landed 

 of 20 cm. during the winter months, and of 22 cm. 

 in the summer months. Now one must con- 

 sider rather carefully what is meant by "over- 

 fishing." The natural problem that confronts sea- 

 fishery authorities is to get as great a quantity 

 annually of niarketahle plaice from the North Sea 

 as this area will afford without progressive deple- 

 tion of its resources. The commercial value of 

 this annual yield must not alone be considered, 

 nor the relative value of one fraction of it (large 

 plaice) as against another fraction (small plaice). 

 Other questions incidental to the general one, such 

 as the effect of the proposed legislation upon the 

 commercially unorganised smaller inshore fisheries, 

 must also be considered. These considerations 

 are, of course, not relevant to Dr. Masterman's 

 discussion, but they ought to be in the minds of 

 readers of these important papers. J. J. 



