POLLOCK IN BAT OF FUNDY 115 



SESSIONAL PAPER No. 38a ' • 



following manner: The envelopes, each containing the scales of a single fish, were 

 arranged in the order of the standard lengths of the fish; the scales from every fourth 

 envelope were examined and the number of rings counted. In this way, without exam- 

 ining scales from all the fish, scales from a representative sample of the catch were 

 examined. The numbers of fish in each year class are shown in table S. The mean 

 standard length of the 5-year old fish of the class of 1910 was 63-9 cm., and that of 

 the 6-year-old fish of the class of 1909 was 67-4 cm. The mode on the 1915 frequency 

 curve is therefore seen to be due to the greater frequency of the 6-year-old fish of the 

 class of 1909, or the same which gave rise to the most prominent mode in the 1914 

 frequency curve. The mean standard length of catches 1 and 2 is 6^-5 cm., and the 

 mean total length is 72-8 cm. 



The material for the study of the pollock of three winters and over, in 1916, consisted 

 of measurements of thirty-two catches made near Campobello island between July 10 

 and October 16. The first eleven of these catches, Nos. 2 to 18, were measured by the 

 writer, both the standard and the total length being recorded and scale samples taken 

 from each fish. The remaining catches were measured by Capt. Sheppard Mitchell of 

 ti.e Biological Station staff, and the total lengths recorded. The dates and locations of 

 the catches and the number of pollock they contained are given in table 9. 



The length frequencies of these catches have been tabulated and catches grouped 

 according to the date of capture. Catches 2 to 12 were made betwen July 10 and 14; 

 their standard length frequencies are given in table 10, columns I to X. From column 

 IX it can be seen that the mode for these catches is about 66 cm. The mode for catches 

 15 to 18 is seen from column XIV to be also 66 cm., although the frequencies of the 67 

 and 68 cm. classes are also large. Catches 2 to 18, which contain 567 fish, have been 

 combined in columns XVI and XVII, which give the length frequencies in per cent. 

 These columns show that the mode, in this case, is to be placed at 67 cm. The mode at 

 67 cm. is slightly in advance of the mode of the 1915 curve which is at 6-6 cm. 



In the case of the remaining catches, numbers 41 to 62, the total length only was 

 recorded. The catches are grouped according to the time of capture, July, August, first 

 half of September, latter half of September, and October. In each of these groups the 

 combined length frequencies of the separate catches, the per cent length frequency 

 obtained by reducing the combined frequencies to per cent of the total number of fish 

 concerned and the per cent frequency in classes of 2 centimeter intervals are given. The 

 later percentages are each obtained by adding two of the percentages of the previous 

 column. They are entered opposite the length of even number althougl^ they really 

 correspond to a length which is the mean of the length of the two classes, the percentages 

 of which were added, e.g. in column IV the per cent 8-0 corresponds to a length of 

 63-5 cm. The percentages in 2 centimeter classes are given because they make possible 

 a more rapid inspection of the table. From table 11 it will be seen that the mode for 

 catches 2 to 18 is 74cm., which may be taken to be the total length corresponding to 

 67 cm. The mode for catches 41 to 6-2 is at 80 cm. and it will be noted that this is 

 approximately the mode of the separate groups of catches. The total length 80 cm., 

 may be considered to correspond approximately to a standard length of 67/74 x 80 cm. 

 or 72-5 cm. 



During the summer of 1916, pollock were scarce around Campobello island, but 

 they became more plentiful in the autumn. The catches 41 to 62 measured by Captain 

 Mitchell are therefore regarded as more typical. It is these measurements which I have 

 used in constructing the curve for 1916 in the graph. As these were measurements of 

 the total length and the measurements for 1914 and 1915 were of the standard length 

 the curve has been moved in the diagram so that its actual mode at 80 cm. comes at 

 72 cm. This has been done merely for the purposes of comparison. The form of the 

 curve for total lengths is of course different from that for standard lengths. It is also 

 to be considered that this curve represents fish caught later in the year than those used 



