Figure I shows that the optimum fishing intensity must be about 

 75 percent of the fishing intensity that prevailed during 1933-35 o 

 From the empirically determined values for the decline of the haddock 

 stock (Raitt, 1939) we can calculate that during the period 1930-35 

 the total yearly mortality was 70 percento If we estimate the natural 

 mortality at 10 percent, a fishing intensity of 60 percent remains « 

 Therefore, the optimum fishing intensity would be 45 percent, the 

 total mortality 55 percent© As long as this mortality is not exceeded, 

 it will be necessary to spar® all haddock up to 21 centimeters to 

 retain a sufficient production© - 



Now we still have to see if it is rational to order a larger 

 minimum size for economic reasons o According to Bowman (1932) the 

 ratio between weight increases and intake of food during a given 

 period increases until the sixth year, that is up to 37 or 40 

 cemtimeterSo 



The progress of prices, as it was before the war, shows that 

 the price per kilogram also increases with the age of the fish© It 

 is therefore profitable not to oatch too young haddock, although 

 one also may not let them get too oldo For instances 



1946 Average 1933*»38 



Small haddock III (21 - 25 cm) f 0.19 f 0e08 



Small haddock II (25 - 30 cm) *• 0o26 » 0ol2 



Small haddock I (30 = 37 cm) »» 0o34 « OdS 



Small medium haddock (37 - 44 cm) " OUl * Oo30 ^ = guilder 



Large medium haddock (44 - 50 cm) * 0o49 * Oo36 



Large haddock (larger tiamSO cm)* 0o49 * 0o38 



Economically, therefore, it is desirable to let haddock live 

 until they have reached a length of 21 centimeters o 



To be able to see how the protection of young haddock may be 

 brought about, we first have to observe the life history of the 

 haddock o 



The haddock stock in the North Sea may be assumed to be practical- 

 ly independent© The most important breeding places are near the 

 Shetlands, the Viking Bank, the Coral Bank, and near the Rockall 

 Banko The spawning time is around March© The haddock concentrates 

 then in an area, roughly between the Moray Firth, the Hebrides, the 

 Shetlands and a line from the Viking Bank to the fishing grounds 

 and from there to Moray Firth© The largest and oldest fish are near 

 the north and northeast side of this area; the nearer one gets from 

 there to the Moray Firth the younger are the haddock which are caught© 

 After the spawning begins they move to the feeding grounds where the 

 school divides itself© A part goes to the northwest and remains 

 there in the neighborhood of the Rockall Bemk, Shetlands and Orkneys 

 and south to the neighborhood of the Moray Firth© The other part 

 goes more or less far into the southern part of the North Sea© The 



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