We now know that 34 million eggs are sufficient to produce 1,000 

 one-year-old haddocko If the 1,970,600 X eggs, produced by a total 

 mortality of 50 percent, will produce 1,^00 one-year-old fishes, then 

 1,970,600 X must be equal to 34,000,000j consequently, X has a value 

 of 17, If^we assume there are as many males as females~(probably an 

 incorrect hypothesis insofar as data are still missing), then the 

 total strength of group VI is 34c With the decrease of 50 percent, 

 there must have been 1,088 haddock during the first year. With this 

 degree of mortality the stock can, with some protection for the 

 fishes after their first year, produce enough eggs to maintain itself o 

 Practically, this condition would depend on a minimum size of 19 

 centimeters. 



With a total mortality of 60 percent, X = 11» The strength of 

 group VI therefore is 22, To retain 22 fi¥h in the seventh year with 

 a yearly decline of 60 percent, one must start with 2,158 one-year= 

 old fisheso The egg production is only sufficient for 1,000 one-year- 

 old fishes. However, if one protects those 1,000 one-year-olds in 

 such a manner that at least 863 fishes are left at the beginning of 

 the third year, then one can allow the fish stock to decline 60 

 percent annually without damaging the level of the egg production. 

 This means that during the second year the haddock stock may decline 

 by 14 percent. This is somewhat more than the natural mortality? 

 actually, therefore, the whole I-group must be left unfished. 



To find the minimtmi size, the length of the haddock at the 

 beginning of the third year has to be knowno That length will depend 

 on the rate of growth, which again is dependent on the density of 

 fishing. In the future we want to strive to retain the density at 

 about the optimum value. Such a density was reached about 1925, 

 If, for the rate of growth of the haddock, we accept the value 

 reached during the period 1925=30 (Raitt, 1939) then the minimum 

 size will have to be 2 3 centimeters. 



Along the same path of reasoning we arrive at the result that 

 with a total yearly mortality of 75 percent, the 1,000 one-year- 

 old fishes must be protected until halfway into the third year, so 

 that at the beginning of the fourth year not less than 440 will be 

 left. In that case it is necessary that no haddock below 27 centimeters 

 be caught. 



The above demonstrates clearly the very important fact that the 

 biologically determined minimum size becomes larger when the fishing 

 intensity is increased. The consequence is that a minimtcn size does 

 not reach its purpose if the fishing intensity— to which this minimum 

 size has to correspond--does not remain constant at the same time. 



5f 



