APPENDIX A: PETTERSSON _. 22 — 



hydrographie changes and fish-migrations extends far beyond the precincts of the North 

 Sea into the Norwegian Sea and northern Atlantic. The origin of these variations is the 

 akernate encroachment of Arctic and Atlantic water upon the littoral shoals and plateaus 

 of the Barentz Sea, the Scandinavian peninsula and the North Sea. 

 Periodicity of In Spring wheu the Atlantic flooding subsides, the Barentz Sea is invaded by Arctic 



the Barenîzsèl "^^^^^ and the fisheries off the Murman Coast cease. Further north in the vicinity of 

 the never-abating flows of the North Cape current good catches of cod, etc. can still be 

 made with the trawl. With the setting in of the Atlantic flood a vast immigration of 

 food-fishes into the Barentz Sea takes place. The food-fishes frequenting these parts 

 therefore have the character of "South-fish" rather than of "North-fish". In the autiamn 

 1902 this immigration of fish from the Norwegian into the Barentz Sea was studied 

 in all its phases by means of fishing-experiments in the deep channel extending from Nordkyn 

 eastwards into Barentz Sea ^ The fishery conditions of the Barentz Sea have been minutely 

 examined through the scientific fishing-cruises of the Russian Commission. In summer 

 and autumn, when circumstances best favour the sojourn of our "North-fishes", there is, 

 however, a vast region to the east of this sea, in which all attempts with the trawl 

 prove fruitless. This is the region of pure arctic water. In the chart on pag. 3 the 

 compass of the trawling in summer and autumn according to Russian data^ is given. 

 Could similar lines be traced for the spring-fisheries, their position would be somewhere 

 in the west part of that sea. 

 Longiineflshery Qj-, jj^g slope of the Notth Sea plateau towards the deep of the Arctic sea, the core 



on the North 



Sea plateau in of the Atlantic current is found all the year round from surface down to a depth of 

 summer and in -00 — 8oo m. In the two sectious On pag. 9 the isohaline 3V2S°/oo outlines a cros- 



the Skager Rail ^ . , , » , 3J J /oo _ 



in winter sectiou of the Current. Underneath the Atlantic current and separating it from the cold 

 arctic bottomwater is the layer, whose opulence in Copepoda and fish is mentioned on 

 pag. 20. Here in summer the Swedish fishermen carry on their fisheries by line close on 

 Shetland in 1 50 — 200 m. depth. In the hydrographie sections it is evident, that the 

 position of this layer in June is closer to the surface than in autumn. To the latter 

 period the fishermen are obliged to set their lines further north and at greater depths, 

 300 — 400 m., in order to catch the ling, the hahbut a. o. In winter when the Atlantic 

 flood subsides and Arctic water predominates, these fishes are caught in the Skager Rak. 



Recent investigations has proved beyond doubt, that the hydrographie, periodicity 

 exercises influence on the return of the trawhng in the North Sea. The fishery statistics 



' K. Dahl, Fiskeriforsog med Skolpen. 



2 L. Breitfuss writes : "The biologj' of the Murman Sea is the outcome of above-mentioned liydrologic 

 elements. As soon as the temperature of this sea sinks below zero , the bottom-fauna undergoes a 

 complete transformation. The trawling outside the Gulfstream area had as a rule but negative results. 

 ... As a rule the food-fishes remain at the Murmancoast and the fjords from May to the end of October, 

 when they again in a northwesterly direction seek the open sea." (Vortrag, printed in; Verhandlungen 

 des V. Internationalen Zoologen Congresses. Nachtrag). 



3 Professor Henking's paper on the Fishing in the North Sea by German trawlers (Mitteilungen des 

 deutschen Seefischerei-Vereins No. i, 1901) bears evideuce to this statement. Professor H. divides the 

 foodfishes of the North Sea area into summer- or winter-fishes, according to the season (Winter = Nov. 

 — April, Summer = May — Oct.), to which they appear in greatest number (see tables pag. 15 et sequ.). 

 Henking's "winter-fishes" are identic with the "North-fishes", his "summer-fishes" with the "South-fishes". 



