LIFE HISTORY OP LAKE HERRING OF LAKE HURON 



379 



values is very close. It appears, then, that in the lake herrins: taken just before 

 spawning in the fall of the year the length-weight relationship can be expressed 

 satisfactorily by the formula W=lc.U, in which Tc has a value of 0.01126. 



Table 46. — Comparison of the theoretical u'eights, computed from the length-weight formula, with actual 



weights of lake herring 



The above it value applies only to the lake herring taken in the fall of the year 

 just before spawning. There is, as D'Arcy Thompson (1914, p. 100) points out, a 

 "regular periodic variation with the course of the seasons" in the value of k, for with 

 unchanging length the weight of the fish falls off after the spawning and winter period. 

 It follows that a study of the fluctuations in the Jc value through the year furnishes us 

 with a sensitive indicator as to the condition of the fish and as to the season of spawn- 

 ing (its beginning and end) "without ever seeing a fish spawn and without ever 

 dissecting one to see the state of its reproductive system." 



RELATIVE ABUNDANCE OF MALES AND FEMALES 



Jarvi found that of 5,765 individuals of the species Coregonus albula L. collected 

 during eight years, 73 per cent were males and 27 per cent females. According to 

 Jarvi, Surbeck (1913) obtained similar results for certain Swiss species of the genera 

 Coregonus and Salnio. The latter found that in a large number of Salmo salvelinus 

 72.2 per cent were males and 27.8 per cent were females; but Hefford (1909) found that 

 in the plaice (Pleuronectes platessa) both se.xes were equally well represented in any 

 large collection. Jarvi correlates the relative abundance of the two se.xes in his mate- 

 rial with Mendel's Law. "All heterozygotes and half of the homozygotes are males, 

 while only the other half of the homozygotes are females. Consequent^, the relative 

 abundance of males to females is expressed by the ratio 3:1, or 75 per cent males to 25 

 per cent females [p. 204]." Gilbert (1922) found that in the sockeye salmon the rela- 

 tive number of males and females may vary with the river basins, the calendar years, 

 the age groups, and with the dates during the course of a season's run. In general, 

 the males showed a decided tendency to precede the females in the spawning migration 



