During the period 1903=40j, the average catch consisted of 

 32 percent haddock,, 12 percent plaice, and 56 percent of other 

 species o After the introduction of the proposed protection, 

 95 percent of the catch of haddockj, 93o4 percent of plaice^ and 

 97o5 percent of other species will consist of marketable fisho 

 If we place the total quantity of marketable fish at X then? 



100 _ 32 y . 100 „ 12 y + 100 ^56 ^ _ ^q^, r,nn nnn v^i«„.,.o™= 

 -95 ro^^ -Szg 166^ W;5 100^' 392.000,000 kilograms 



or X is 377;, 000s 000 kilograms o This then would be the amount of 

 the optimum catch of marketable fish© If the fishing would have 

 b«e|n carried on in the same way as ha4 been done during the period 

 1933=35, then the optimum catch would have amoxinted to only 

 SSOjOOOjOOO kilograms o To arrive at this figure^ it is necessary 

 only to take the amounts corresponding with that period for the ' 

 percentage of undersized fishp from table 8 in the above fonnulaj 

 to replace the percentages now used© We get theng 



100 32 X + 100 X ^2 X + 100 56 -. ^ ^qo qoO 000 kilograms 



W JUG- -^ '^ 15© ~ "95 Too ~ 39^.000.000 kilograms 



Tlaere appears to be an optimum catch at a fishing intensity 

 of not quite 40 percent© The size of the catch is 390,000,000 

 kilograms and 370,000,000 kilograms of that amount can be qaught 

 as marketable fish, if the protection here proposed is introduced© 

 If the younger fish are less protected, then a higher percentage 

 of undersized fish and smaller returns will result© 



5© Conclusions and Summarj 



Proposed Regulations for the North Sea 



We enumerated in detail the amount of the optimum catch for 

 the North Sea and how great the benefits or disadvantages would 

 bo by changing the mesh widths or by the introduction of a minimum 

 size fish© The danger inherent to an enumeration is that the 

 reader may be impressed that these statistics cannot be assailed 

 and that it is certain that the optimum catch from the North Sea 

 is exactly 392 and not 380 or 400 million kilograms© Unfortunately 

 this is not the case, the numbers have only an approximate value i they 

 have the value of an extensively supported estimation© The calcul- 

 SLtion could become more exact if the basic information becomes 

 better known, as for instance better values for the natural 

 mortality, the fishing intensity, and the relation between density 

 and speed of growth© 



The studies on overfishing in the North Sea and the fight 

 against this overfishing are generally not characterized by a large 

 amount of quantitative information, I have found this a difficulty 

 because the questions connected with growth and productive power 



