CANADIAN FISHERIES EXPEDITION, 191>rl5 105 



blenis suitable for treatment by statistical methods of work, and to procure adequate 

 observation material for statistical investigations. The question as to what problems 

 can be dealt with will largely depend upon the possibilities of obtaining material for 

 observation, in which respect, different waters will be found to vary, as we have here 

 to reckon both with the technical features (implements used, intensity of the fishery, 

 etc.) and also with natural conditions, which are not every^vhere alike. In the case 

 of each area investigated, therefore, it will be necessary to test the possibilities and 

 limitations of the methods, i. e., to gain experience by actual application of the 

 methods on the spot, and to utilize the results obtained by the work in determining 

 the possibilities of continued operations, and in drawing up plans for the same. On the 

 other hand, such determination will naturally be facilitated when it is possible to 

 compare the results of preliminary investigations in a new area with the experience 

 furnished by similar work elsewhere, which renders it easier, for instance, to distin- 

 guish between generalities and specific local features. In the following pages, there- 

 fore, an attempt will be made to sum up conclusions as to the possibilities for obtain- 

 ing material of a typical and representative character acquired during the Norwegian 

 herring investigations, which have now continued over a period of ten years. 



First, as regards the age composition of the Norwegian herring stock, the inves- 

 tigations distinctly show that the stock in question does not appear as an even mixture 

 of every possible age-group; on the contrary, it is seen to be divided up into several 

 more or less markedly separated groups. These groups correspond in some degree to 

 the various " sorts " of herring, as known and distinguished by the fishermen, and the 

 appearance of the various groups at different places and times gives rise to various 

 kinds of herring fisheries. The most distinctly defined group is that containing the 

 mature fish, known by the fishermen as "large herring" when taken before spawning, 

 •and "spring herring" when captured on the spawning grounds and ready to deposit 

 their spawn. Another group is the " fat herring," which may be characterized as 

 herrings of moderate size still immature, and of excellent quality, whence the name. 

 A third group is that of the " small herring," i.e., small, young, immature fish, of 

 poorer quality than the fat herring. The habitat and migration of the various groups 

 are evidently different. The spring herring, for instance, crowd in to the west coast 

 in enormous numbers during the first months of the year. The fishermen have a 

 characteristic name for these close-packed shoals; they call them " sildebjerg "=a 

 " bjerg " or mountain of herring. It is a rare thing to find a young, immature fish 

 among these masses of mature, " full " herring. And on the other hand, fish with 

 genital products already developed are rarely found among the fat herring taken in 

 the northern Norwegian waters during autumn. 



The individuals in a year-class move up, so to speak, from group to group as time 

 goes on, and as their development proceeds. The movement, however, does not take 

 place simultaneously in all individuals, so that a particular year-class may become 

 divided up, and fish of the same age will be thus encountered at different places and 

 times, in association with those of various other ages. The Norwegian herring mate- 

 rial offers several instances of this spreading of a year-class over different groups. In 

 1908, 1909, and 1910, fish of the 1904 year-class were found both among the mature, 

 full, herring on the west coast, and among the immature fish in the northern waters, 

 vide Hjort (Y) and Lea (XI). The investigations upon immature herring, in 1915, 

 showed that a distinct age-group occvirred within a restricted area, and at the same 

 time, associated partly with younger, partly with older, but still immature fish. This 

 feature will be seen illustrated in table 3. 



It is apparent from table 3, that the fish 2i years old are in two samples 

 associated with almost exclusively older fish (one year older) whereas in the two 

 others, they are found in company with others, almost without exception younger 

 (one year younger). In the one case, they make up about two-thirds of the total 

 number in the sample; in the other, less than a third. 



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