HOEK— INTRODUCTORY , _ X — 



development of the 5'oung cod, their natural history during the first year, and 

 the later stages and migrations of this fish. Some gaps still occur here and there, 

 but in many ways it must be regarded as an enrichment of our knowledge of 

 this extremely important fish. Interesting observations have been reported, especi- 

 ally with regard to the migrations of the cod. The answer to the question, which 

 is of greater importance for the Norwegian fisheries than for those of the North 

 Sea, viz. where the large cod frequent during the months in which they are not 

 found on the coastal banks, seems to be, that they wander far out into the 

 Norwegian Sea and are distributed pelagically over a large area of the ocean and 

 over water-layers of considerable depth. At this time they feed upon forms which 

 lead a pelagic life (especially such fish as herring and lodde). 



Henking's views A hypothcsis similar in the main has been expressed by Prof. Henking 



(Hanover) for the North Sea, namely, that the large cod, which spawn in winter 

 on the coastal banks, are pelagic in summer over the deeper North Sea banks. 

 He thiis believes, that they do not leave the North Sea; with the assistance of 

 the statistics for a number of German steam-trawlers, the same author has reported 

 on the distribution and migrations of numerous other North Sea fishes to the 

 meeting of the International Council in February 1904 (Hamburg). This report 

 appears as Appendix F to this General Report. 



Fulton's discovery If we add to this, the interesting discovery by Dr. Wemyss Fulton (Aber- 

 deen), that spawning cod occur in autumn at a certain part of the North Sea, as 

 also the detailed picture of the developmental history and occurrence of the cod 



Heincke's report iu thc North Sca, procurcd by Prof. Heincke (Heligoland) from the investigations 

 carried out especially by the Germans and reported on here in Appendix E of 

 this General Report, it may certainly be said and with satisfaction, that the inves- 

 tigations of the first two years have contributed in a marked manner to the 

 increase of our knowledge of the natural history of this species. 



With regard also to the other migratory fishes and the problem of migration 

 in general the reports just mentioned of Prof. Heincke and Prof. Henking maj' 

 be consulted with interest. For so far as these papers bear on the present problem, 

 their contents may be summed up as follows. 



Henking's results The rcsults reached by Prof. Henking are: 



The fluctuations in the curves representing the catches of food-fishes can 

 only be explained on the supposition, that the number of the fishes in front of 

 the trawl actually varies. Migration may take place in two directions: vertical 

 into higher or deeper water or bottom-layers not reached by the trawl, horizontal 

 into other parts of the sea. For the various fishes, the author then comes to the 

 following conclusions: 



The haddock is a summer fish i.e. caught in greatest quantities in summer; 

 the most probable explanation of its occurrence in increased quantities in the 

 summer, might be that it seeks the water-layers on the bottom more in summer. 

 With regard to the hake, the supposition of an inward migration on a large 

 scale is highly probable. It is practically not taken at all in the first three to 

 four months of the year, then it appears in ever increasing numbers — perhaps 

 with the inflow of Atlantic water. 



