CAyADIAy FISHERIES EXPEDITIOX, lOl'rlo 115 



B. SPECIAL. 

 THE CANADIAN MATERIAL. 



X, Description A^D pkeluiinary grolpixg of the Caxadux materl\l. 



The chart, lig. '2>i, ou page 117 will serve to locate the samples placed at my dis- 

 posal and dealt with in this chapter. The material comprises a large number of 

 samples from au area embracing the Atlantic coast of Canada, the gulf of St. Law- 

 rence, and the coast of Newfoundland. 



The comparatively large number of samples, and their distribution throughout 

 different seasons, counterbalances, at any rate in the case of certain waters, the dis- 

 advantage arising from the fact that the number of individuals in each sample is, as 

 a rule, but small. It will, however, probably be desirable in the case of future investi- 

 gations, to secure larger samples, as the stock in these waters has been found to in- 

 clude an unusually large number of age-groups. Nowhere have fish of so great age 

 been found in such considerable numbers as here. 



Bj' far the gTeater portion of the samples originates from catches made with 

 implements, viz., gill-nets, which cannot be regarded as particularly suitable for the 

 purpose ol obtaining representative material. As mentioned in the foregoing, samples 

 of netted herring must necessarily be less reliable tlian samples taken with non-select- 

 ive implements, especially where no opportunity occurs of making comparison, as in 

 Norway, with samples of the latter sort. Some doubt may therefore arise as to whether 

 the younger and smaller fish are represented in their due proportion in the sam- 

 ples. There are, however, as will subsequently be shown, certain peculiarities in con- 

 nection both with age-distribution and growth, which cannot be explained as merely 

 resulting from the selective effect of the nets. 



In addition to the samples of grown herring from various places and taken at 

 various times, we have also a number of samples of young, immature fish, drawn 

 partly from catches made by steam drifter No. 33 with the drift-net, during the sum- 

 mer of 1915, and partly also from trap-catches. The importance of these samples of 

 immature herring lies not so much in their representative value, which may be oi)en 

 to considerable doubt, not only on account of the method of capture, but also because 

 the experience gained in the course of the Norwegian investigations has shown that 

 some caution is necessary when dealing with samples of quite young herring. They 

 form, however, a valuable supplement to the material of gro^vn fish, as furnishing an 

 aid to to the determination of the time when summer growth begins, and also because 

 it has been found that these young fish exhibit growth variations for the different 

 waters exactly similar to those noted in the case of the grown individuals. These 

 young samples, therefore, add to the value of the remaining material, and give the 

 results a more general character. 



From the very first, on going through the scale-samples it was strikingly evident 

 that the material must embrace several different, in some cases strikingly different, 

 "sorts" of grown herring. The difference between fish from the different localities 

 made itself apparent partly in the more or less distinct marking of the annual rings 

 on the scales, rendering number and distance more or less easy to read, partly in the 

 fact that the dominant age-groups (year-classes) differed in samples from different 

 localities, and finally, in the different character of the growth, as indicated by the 

 scales. It therefore seemed natural, after this first survey, to make a preliminary 

 division of the material according to locality. This gave four groups of samples, as 

 follows : — 



