LIFE filSTORY OF LAKE HERRING OF LAKE HURON 



337 



(1914) and others. This law states that those fish that gi'ow most slowly during the 

 earliest years of life grow most rapidly during the later years of life, and vice versa. 

 Later (p. 370) I shall show that this principle actually holds for the lake herring. This 

 law would still leave unexplained why the increments of the first two years of life 

 tend to be least in the sixth age group of a year class, but it would account for the 

 rapid growth of these fish later in life. So, also it may account for the fact that 

 the third-year increment of the 5-year fish of a year class is not less than that of the 

 4-year fish. 



To recapitulate, of Miss Lee's seven suggestions (p. 328) only the first is accept- 

 able in explanation of her "phenomenon" in the scale diameter and computed body- 

 length measurements of the lake herring. That the herring that reach sexual matu- 

 rity late in life are the smaller individuals of their year class appears highly probable 

 from the data of the Oscoda fish (p. 390). This fact would explain why the scale 

 diameters of the fish of a younger age group of a year class generally exceed in length 

 those of the fish of an older group; but it could not explain the progressive increase 

 with age in the scale and body increments of the later years of fife. To account for 

 this, two other factors were considered — sexual maturity and compensation in growth. 

 It was stated that in fish (at least in the northern species) sexual maturation usually 

 is accompanied by a retardation in the growth of bod}^ and scale and that a compen- 

 sation in growth occurs; that is, fish that grow slowly during the earliest years of life 

 grow rapidly during the later years of life, and vice versa. Virtually all the data of 

 Tables 22 and 23 on the increments of scale and body growth can be brought into 

 agreement and quite satisfactorily explained by these three factors. In fact, only 

 the first and third factors are required to explain all the data; but, inasmuch as the 

 second one (sexual maturation) is also actually involved, it can not be ignored. Lee's 

 "phenomenon," then, in so far as the lake herring are concerned, seems to be largely 

 the result of perfectly natural events in the life history of the fish. 



Table 24. — Uncorrected and corrected {by Lee's Jormula) computed lengths nf various year classes oj 

 Saginaw Bay herring for each year oj life. Identical fish were used for both series. 



• The last value of each age group represents actual body measurements. 



