168 DE PANT M EXT OF THE NAVAL SERVICE 



luade from measurements of such small lots of individuals. All three show in their 

 curves summits at 19 cm. Two show summits at 15 cm., and the third a definite step 

 in the curve at 15 cm. Only one shows a summit at 12 cm., the other two samples 

 having no individuals of that or neighbouring sizes. Summits (or steps) are therefore 

 quite constant for the same age group in the same locality at any one time. 



These examiples will serve to show the manner in which the results of the measure- 

 ments have been interpreted. 



To determine the rate and period of growth of each of the different age groups, 

 the representative length of each group, in each of the samples from Passamaquoddy 

 bay in which it was represented in sufficient numbers, was determined in the manner 

 described above. These lengths have been plotted against the dates on which the sam- 

 ples were obtained, in fig. 2. For each group a curve has been drawn connecting the 

 circles that indicate the length of the group at different times. Where there are con- 

 siderable gaps the curves have been continued with interrupted lines. There are occa- 

 sional points that do not fit into the general scheme. Those of November and 

 December, intermediate between B and C we have already interpreted as due to more 

 or less complete fusion of B and C. 



The fresh fish measure somewhat larger than the salted. For this reason the 

 lengths in the samples of May 24 and September 16, seem high compared with the 

 others. The samples of June 15 and November 3, show groups with mean sizes of 

 12-5 cm. and 18 cm. respectively. In these cases we may have group C of the preced- 

 ing year which has failed to fuse with B of the same year, whereas in A these two 

 groups are constantly fused. 



In fig. 2 we have a graphic representation of the growth of the three groups A, B 

 and C during the year. The period of growth for A and B is from May to the end 

 of September. For C the beginning of the period is not shown, as at that time the 

 fish were too small to be taken by the nets. It appears to continue later for this group, 

 at least well on into October. The rate of growth for B and C is somewhat less than 

 2 cm. a month in the middle of the summer when the growth is most rapid. The rate 

 for A is less, about 1-5 cm. a month as the maximum. 



In many of the samples larger fish were present, but their numbers are so small 

 as to be unsatisfactory for. a determination of their Tiiean sizes and growth. The little 

 evidence there is, shows a group beginning at 1!) cm (April 16 and May l^i!) and grow- 

 ing to 23 cm. (October 14, October 25, November 10, and December 6). Also a group 

 reaching 26 cm. by September 7. 



The determination of the ages of these groups presents difficulties. Groups B and 

 C are quite evidently less than one year apart in age. The lack of material less than 

 7 cm. in length must leave the question in doubt but it is most reasonable to suppose 

 from the rate of growth shown in 1915 that group B, beginning at a length of 8-5 cm., 

 must have already passed through a full season's growth. The well-established fact of 

 decrease in growth rate with increasing age would necessitate this interpretation, 

 unless there were still greater growth during the first year. We would then reach the 

 conclusion that group B was spawned in the spring of 1914, reached a length of 8-5 

 cm. by winter and in 1915 grew 6-5 cm. to a length of 15 cm. Group C would have 

 been spawned in the fall of 1914, have reached a doubtful length by winter, perhaps 

 5-5 cm., and in 1915 grown perhaps 7 cm., reaching a total length of 12-5 em. 



Group A is evidently in its third summer and consists of a mixture of both 

 spring and fall spawned fish. In the third year, therefore, the herring grow from a 

 length of 14 cm. to a length of 19 cm. The group growing from 19 cm. to 23 cm. 

 would consist r f hf'Tring in Iheir fourth year and those reaching 26 cm. of perhaps five 

 year old fish. 



