OF THE NORWEGIAN FISHERIES : A REVIEW. 69 



" feeding migration," and takes place at the mouth of Christiania fjord 

 iu autumn (November). 



The movements of the herrings during this fishery are determined, 

 according to Hjort, by the movements of the bank waters at this season. 



Thus, iu November, 1893, the Baltic current was dammed up in the 

 Cattegat, and warm bank water (11° to 12° C.) flowed from the Norwegian 

 channel between all the islands at the mouth of the Christiania fjord. 

 The herrings then abounded. At the same time the "prey of the 

 herring," the Diatom Chcctoceros, was abundant. 



In November, 1894, on the other hand, Baltic water covered a much 

 larger area, and bank water was both of less thickness and deeper down. 

 Along shore the Baltic current was 50 metres deep, though further from 

 shore (a few miles) it was very thin. Herrings abounded at sea (16 to 

 20 miles off), but would not venture in between the islands and the laud. 

 The fishery was largely a failure. The food of the herring {Chcetoceros) 

 was not met with in the upper layers (0-10 metres), though it was 

 present at greater depths, and was abundant further out to sea, many 

 miles from the coast. 



It will be remembered that Pettersson has also remarked upon the 

 coincidence of the autumn herring fishery in the Cattegat with the 

 arrival of bank water of salinity 32 per thousand to 33 per thousand, but 

 according to him this arrival may occur as early as August and 

 September. He discriminates between an autumn fishery (August and 

 September), due to the arrival of the Danish bank water of high 

 temperature, and a winter fishery (October or November to February 

 or March), due to the arrival of Norwegian bank water of low tempera- 

 ture. The former fishery is carried on by means of floating nets 10 to 

 20 miles from shore, the latter by means of nets (seines) along the 

 shore. But I have already shown in this paper (p. 62), when dis- 

 cussing the nature of bank water, that the sharp distinction drawn by 

 Pettersson in regard to the bank waters is difficult to understand, since 

 the temperature of undoubtedly Norwegian bank water in the eastern 

 part of the Skagerack in November may extend from 8° to 12° G. It 

 is equally doubtful whether there is any racial diflerence between the 

 autumn herrings caught in warm bank water and the winter herrings 

 caught in cold bank water. Pettersson shows that quantities of herring 

 arrive with the former in August and September, and that the winter 

 herring fishery ceases as soon as the bank water is swept out by the 

 Baltic current in the spring. The fact that the first bank water to enter 

 the Skagerack in the autunm has a high temperature and that subse- 

 quent inflows of bank water have a lower temperature is explicable 

 without the necessity of assuming that the former is of southern and 

 the latter of northern origin. Both may be of northern origin, since the 



