LIFE HISTORY OF LAKE HERRING OF LAKE HURON 301 



The above review indicates that the large majority of the experiments on the 

 scales of fishes favor, as far as they go, the age hypothesis. It is a question, however, 

 in certain cases at least, in how far the interpretation of the scales of the experimental 

 fish was influenced by the known history of the specimens. We know, for example, 

 that Hintze's interpretation rested entirely upon such knowledge. Or, again, in 

 the case of Fraser's (1918) or Snyder's (1921) 4-year-old salmon it appears dubious, 

 as judged from the photomicrographs of the scales, whether one wholly ignorant of 

 the fish's history could interpret correctly its scale with absolute certainty. The 

 failure of an annulus to form so as to be recognizable was in every case (Thomson, 

 1904; Menzies, 1912; Peart 1922) ascribed to an abundant supply of food. 



CORRELATION BETWEEN GROWTH OF BODY AND SCALE 



HISTORICAL 



Walter (1901) first announced that the relative length and width of a growth 

 zone on a scale expressed to a certain degree the relative intensity of body growth, 

 designated in terms of length and height. (See quotation, p. 296.) He measured 

 the shortest diameter included in each growth zone of 20 scales from each of three 

 races of commercial pond carp in their third year. As the growth history (that is, 

 the average weight, height, and length) for each year of life of these races was known, 

 Walter was able to compare the average length of each growth zone on the scales 

 with the average weight, length, and height of the fish for corresponding years and 

 discover that the growth of scales is correlated with the length and height of the 

 fish and not with its weight. Expressing the average weights of carp for the first 

 three years of life in the form of a ratio, he obtained the values 1:10:30 as against 

 the values 1:1.5:0.67, which express for corresponding years the ratio of the aver- 

 age widths of the zones on the scales. (The author should have employed the ratio 

 of the average diameters; namely, 1:2.5:3.2.) However, as a rapidly growing race 

 of carp attains a length of 7 to 15 centimeters the first year, 25 to 35 centimeters the 

 second, 35 to 45 centimeters the third, and 45 to 50 centimetere the fourth year, it is 

 seen that the ratio of the growth zones on the scales coincides more nearly with the 

 length than with the weight of the fish. 



Thomson (1904) and Seligo (1908) measured each growth zone along the anterior 

 radius but did not compute lengths from their measurements, although the latter did 

 base his conclusion relative to the rate of growth of the species directly on the relative 

 width of each growth zone. Dahl (1907) asserted that the rate of growth could be 

 seen from the width of the zones on scales and illustrated by means of diagrams how 

 one may distinguish autumn from spring herring by the comparatively large first 

 year's growth zone on the scales of the former. 



The first critical and significant contribution to the subject under consideration 

 is that of Lea (1910), who investigated whether "the scale of herring might not be 

 used merely for determining the age of * * * but also for demonstrating how 

 the particular individual's growth had occurred during the earlier growth periods 

 * * * to what extent the different individual scales mutually accorded with each 

 other in their mode of growth, and might be assumed to give the true picture of the 

 whole animal " (Hjort, 1910). From this study the scale formula (p. 272) was evolved. 



