Physiological Changes with Age in Fish 199 



egg production declined (Table III). The values were based 

 on regressions calculated separately for the different age 

 groups. At similar lengths regular increases in fecundity with 

 age occur among ages II, III, IV, and V. Ages VI and VII 

 were combined in the calculations because individuals of 



Table III 



Fecundity of haddock {Melanogrammns aeglefinis) of the 



SAJME SIZE AT VARIOUS AGES. MODIFIED FROM RaITT (1933) 



these ages were scarce in the population. Their fecundity was 

 about five per cent lower than that of age V. At extreme 

 lengths the latter group has a slightly lower fecundity than 

 age IV of the same length. The same result was found when 

 the fecundity of haddock of the same weight were compared 

 at different ages. 



The effect of age was shown to be due to the relationship 

 between fecundity/length and body weight/length. Raitt 

 calculated the first of these comparisons separately for the 

 different age groups. Fecundity increased very rapidly in the 

 youngest spawners of age group II {F = 0-005187 X L*'^^), 

 but was considerably lower in the remainder of the popula- 

 tions, as the remaining equations show : age III {F = 1- 788 X 

 L^-^% age IV (i^ = 1-527 X L^'^^), age V (i^ = 2-069 X 

 L3-21), and ages VI and VII combined (2^ = 1-546 X L^^^). 

 Raitt used Russell's extensive data (1914) on the haddock to 



