8 GEORGE V SESSIONAL PAPER No. 38a A. 1918 



VI 



ON THE AGE AND GROWTH OF THE POLLOCK IN THE BAY OF FUNDY. 



By Professor James W. Mayor, Ph.D., Union College, Schenectady, N.Y. 



(With one Diagram.) 



I. INTRODUCTION. 



The present report represents the results of studies on the age and growth of 

 pollock caught in the Bay of Fundy during the years 1915 and 1916. A report Mr. 

 Douglas Macallum, prepared under the direction of the present writer, then curator of 

 the St. Andrews Biological Station, dealing with the pollock caught in 1914, is already 

 in the press. Mr. Mucallum's report refers particularly to the older pollock of from 

 three to six or more years growth, as determined by their scales. Besides working out 

 the rate of growth of these pollock, he obtained indications that the most frequent year 

 class was that of 1909. Some of the results of this report are included in the present 

 paper for comparison with the data obtained in 1915 and 1916. 



The object of the investigation has been to determine: (1) the distribution of the 

 young pollock, (2) the rate of growth of young pollock during their first two or three 

 years, (3) the relative frequency of the different year classes in typical commercial 

 catches. 



The writer is indebted to the members of the staff of the Biological Station at 

 St. Andrews in 1915 and 1916 for assistance in measuring and taking the scales from 

 fish. He is particularly indebted to Mr. E. Home Ci^aigie for the measurements made 

 in July, 1915, and to Dr. A. G. Huntsman, the curator of the Station, for assistance 

 and advice in obtaining the young pollock in 1916. 



II. — METHODS OF MEASURING FISH AND STUDYING SCALES. 



Two measurements for length have been employed. The standard length is 

 measured from the tip of the snout to the end of the vertebral column (easily deter- 

 mined by feeling with the fingers). The total length is measured from the tip of the 

 snout to the end of the tail, the caudal fin having its normal spread. In the case of 

 firih over 20 cm. in length the measurements are always to the nearest centimeter; 

 ii; the case of the smaller fish, under 20 cm., to the nearest millimeter. The standard 

 length was chosen at the beginning of these investigations for the following reasons: 

 (1) It can be more accurately determined by the ordinary methods, (2) it is not 

 affected by the position or spread of the tail or by injuring the tail, (3) it measures 

 tue actual length of the body of the fish, (4) it has been found by Hjort, in the case 

 cf herring, that a better correspondence between actual lengths and lengths as calcu- 

 lated from the position of the rings on the scales is obtained by taking a length V 

 measured from the anterior end of the pectoral fin to the end of the vertebral column, 

 than by taking the total length. The standard length differs from V by the length of 

 the head only, 'while the total length differs by the length of head and tail. The 

 total length has been recorded for comparison with the measurements of the European 

 investigators who use this length. 



In 1914 the standard length only was recorded. In 1915, for catches No. 1 and 

 No. 2, both the standard and total lengths were recorded, and for catches No. 3 to 

 No. 5 only the standard lengths. In 1916 for catches No. 1 to No. 40, both standard 

 and total lengths were recorded and for catches No. 41 to No. 62, the total length only. 



The scales of the fish were taken in most cases from a region marked by the end 

 of the right pectoral fin when extended along the side of the body in a posterifc)r 



111 



