— 39 — 2- HBLI/AND-HANSRN 



distribution of weights of the different sizes for the general North Sea average 

 catch between October 1902 and October 1906. 



Between 15 and 60 cm. the area included by this curve of weight has been 

 ascertained by planimetry, not only for the whole curve but also for the different 

 groups. The result is an average total weight of 11-9 kilos' per trawl-hour, 

 corresponding with the number previously found, viz 49-4 individuals. This 

 average total weight differs considerably from what is obtained through statistics 

 of the catches made by market-trawlers. The figures in the latter case are bound 

 to show higher values: both because the boats use far larger trawls and also 

 because they choose those places where they reckon on obtaining the greatest 

 weight of fish. And as the capture of the haddock occupies an extremely 

 prominent place in the fisheries of the North Sea, choice of fishing-grounds must 

 necessarilj' depend in the main upon where it will most probably be met with. 



It is not therefore so much to be wondered at that statistics of haddocks 

 landed at Aberdeen give an average weight ' for the North Sea (from about 

 55° N. L,at. and northwards, i. e. the Northerly portion of the North Sea) of 68-9 

 kilos per hour (D'Arcy Thompson), or from six to seven times as much as the 

 average weight here recorded. 



The average relation then between total weights and total numbers is 0-2,2, 

 according to these calculations: or in other words the individual haddock taken 

 with the trawl weighs on an average 0-33 kilos. This weight according to Fulton 

 corresponds with a size of about 29-5 cm., or a length nearly coincident with the 

 average length for Small Haddock. 



We would draw attention to the degree in which our curve of weights differs 

 from our curve of numbers. Whereas the latter reaches a maximum at about 

 24 cm., the curve of weights attains its maximum at 30 cm. The mean lies 

 roughly around 32 cm., so that quite half of the weight is due to individuals 

 below this figure. The reason lies in the fact that the quantity of Large Haddock 

 taken per trawl-hour is small: still even this small quantity has a very great 

 effect upon the weights. 



We can now find the proportion between the weights of the 

 principal different groups, just as we could do when dealing with their 

 numbers: and planimetry shows the weights below and above 21 cm. to be as 

 follows: — 



Unmarketable on an average 0-3 kilos per trawl-hour 

 Marketable — — 11 -6 — — 



Here the weight of marketable is relatively too small, as we have not 

 included in our calculations individuals over 60 cm. We notice that while in 

 the catch about ^j-jth. of the number are unmarketable, this group 

 merely constitutes ca. 740th of the weight. Thus this relatively 

 large number has but a very small share in the value of the catch. 



In the following table we find the proportions of the weight per trawl-hour 

 allotted to the different market-groups as per the limits given on page 18. 



I Individuals larger than 60 cm. have been neglected. 



