OK THE NORWEGIAN FISHERIES: A RbVIEW. (3? 



had reached the southern portions of the Fishery district, fishing for 

 herring was only carried on away from the mainland, e.g., at Utsire, 

 and none between that island and the shore, the explanation being that 

 the intervening channel was occupied by the fresher and colder waters 

 of the Baltic current. Similarly at a later period, in the month of 

 April, the herrings disappeared from the whole district, when the 

 Baltic current, at last released from the Skagerack, had displaced the 

 North Sea water to a depth of 60 metres. 



Hjort does not stop at this point, but proceeds to examine the records 

 of the fisheries for previous years in the light of contemporary data as 

 to the temperature of the sea along the coast. I have already shown 

 in the section on " Hydrography " that Hjort's investigations have 

 established a relation between temperature and salinity during the 

 "typical winter period" {i.e., February and March), so that, within 

 certain limits, the temperature of the water during this period is an 

 index of its salinity. Thus, as a rule, 



6° to 7° C. indicates Atlantic water. 

 5° „ North Sea water. 



4° to 3° „ Bank water. 



2° to 1° „ Baltic current water. 



Upon examination of the records in the light of this assumption, 

 Hjort has discovered the following interesting series of correlations : 



In 1881 (Jan., Feb.) herrings occurred in swarms, but did not come 

 close inshore (except when isolated shoals of them were chased by 

 whales), thus depriving fishermen of the most profitable and regular 

 method of capture, viz., " night netting." Eventually, in mid-February 

 to Alarch, the herrings spawned in deep water (70 and 80 fathoms), 

 away from shore. The temperature of the water during this season 

 was very low — 



2'3° at surface. 



2-7° „ 38 metres. 

 3-3° „ 75 „ 

 4-8° „ 113 „ 



thus indicating a very thick layer of Baltic water of low salinity. 



In 1883 (Feb.), on the other hand, the temperature was high, being 

 5° at the surface, thus indicating the presence of North Sea water. 

 Abundant catches of herrings were made close inshore, even at a depth 

 of 10, 16, and 20 metres, "reminding one of the rich fisheries of olden 

 days." 



In the winter of 1885-6 the temperature was again low. Again 

 the herrings were down at extraordinary depths, where spawning took 



j: -2, 



