A small niimber of females become ripe at the age of Z$ the 

 majority, however, do not become ripe before the age of 3e Therefore, 

 the majority of females will (at the age of 3) produce more than 

 68jOOO eggs the first time they spawn and it may be said roughly 

 that the haddock stock retains its strength ifj on the average 

 each female spawns onceo This is in agreement with a rule accepted 

 by many marine biologists more by feeling than by a collection of 

 facts© In reality it is not necessary that every female spawn, sjnce 

 a number of females spawn several times and the number of eggs increases 

 progressively with their age* 



The number of haddock that were caught by the fishery in one year 

 was 40=50 percent during the period 1918=27, whether they remained 

 in the nets or escaped (BSckmann^l932) e We will define this as the 

 fishing standardo If no fish can escape through the meshes in the 

 nets the fishing intensity (that is the measurement of the percentage 

 of the stock killed yearly by the fishery) has the same value o If 

 escape is possible the fishing intensity has a lower value than the 

 fishing standardo It is now possible, for different values of the 

 fishing intensity, to estimate how long the year classes have to be 

 left alone, if egg production is not to decline o 



This has been done in table 11 for fishing intensities of 40 

 percent, 50 percent and 65 percent, which augmented by natural causes 

 would seemingly give a total mortality of, respectively, 50 percent, 

 60 percent and 75 percento 



"» 



Referring to table 11, the number of females which remained 

 after 6 years of fishing, that is at the beginning of the seventh 

 year, was placed at X* If the fishing standard is 40 percent, and 

 the natural mortality is 10 percent, than half of the available 

 fishes will die during each year. At the beginning of the sixth 

 year there would be 2 X females, at the beginning of the fifth 

 year 4 X etce Therefore, with a total mortality of 60 percent, the 

 number "of females in the sixth year would be 2»5 Xj and with a total 

 mortality of 75 percent it would be 4 Xc " 



The next step was to shorr in X the number of eggs produced by 

 each year class. In table 10, column 6 shows the average number of 

 eggs that the mature female spawns at different age levels? column 4 

 shows the percentage of females that will mature at those age levels o 

 Multiplication of both numbers for each year class shows the number 

 of eggs that the average female, mature and immature together, has 

 at each age level o These numbers, shown in colimin 2 of table 11, must 

 be multiplied by the number of females, shown as X (column 3), to 

 give the iiotiaa ndifebeg of ©g^H i(odi«jnn 4)o 



5S 



