— i6 — 



Several irregularities were found in the original material, chief of which is 

 one around 30 cm. We find a grouping due to the composition of the material 

 itself, a characteristic group around this size being much in evidence in 1903. 

 This group is a little isolated in the average-curve, owing to its earlier stages 

 having been previous to these investigations. The summer groups too are 

 much more prominent than the groups at other seasons of the year (cf. Intro- 

 duction). The completed line in the figure is not the curve obtained directly 

 from the detailed records, but a smoothed curve. This smoothed curve has been 

 used for the analysis that follows. 



As all the catches treated here were made with an ordinary English trawl, 

 we shall not meet with individuals under 15 cm. In a good many of the 

 catches — particularly the English ones — a fine-meshed bag was employed at the 

 bottom of the trawl, by means of which smaller individuals were also caught. 

 But we have neglected them here, and shall confine ourselves to investigating 

 the individuals caught with an ordinary open-meshed trawl. 



The left side of the curve rises sharply to a maximum where the length is 

 24 cm. This part of the curve does not represent the true occurrence of the smaller 

 haddock sizes at the bottom of the North Sea ; even the numbers of fish as long as 

 20 cm. will be insufficiently shown in the material. — While the figure well depicts 

 the composition of the catches made by the research steamers, the curve does 

 not correspond with the actual catches of the market-trawlers or with the 

 quantities brought to land. This arises partly from the trawlers selecting their 

 fishing locality with a view to obtaining large fish, and partly because they throw 

 overboard many of the small fish which are thus not included in the statistics 

 of fish landed. The curve in fig. 4 therefore probably represents better than 

 other statistics could the general composition of the haddock-aggregate in 

 1902 — 1906 in the parts of the North Sea under discussion, subject-however to 

 the two important limitations: that it merely shows the conditions in those parts 

 of the North Sea where the trawl can be used, and that it holds fairly true for 

 that portion only of the haddock-aggregate which is over some twenty odd 

 centimeters. 



Above 24 — 25 cm. there is a very rapid decrease in the numbers of the 

 different lengths, till we come to 40 cm. where the reduction becomes somewhat 

 slower notwithstanding that over 50 cm. there are remarkably few fish. The 

 curve gives roughly the following figures ^ for each additional 5 cm.: 



20 25 30 35 40 45 50 55 60 cm. 

 80 175 no 60 20 8 5 3 I 



Thus for every haddock 60 cm. long there should be almost 200 

 haddocks of the length of 25 cm., more than 50 of the length of 

 35 cm. and abouth 10 of the length of 45 cm. It would have been 



I These figures are only relative and do not mean the numbers per trawl-hour. In this case 

 and in many of the following ones the relative conditions only ought to be considered; I have 

 not, therefore, introduced a vertical scale for the number in many illustrations. 



