Combination. 



251 



ausund and Trondhjcin sliow. tor tlio vcmis isim; l'.m-_>, as cdiii- 

 pared with ISSfi — 95, an avi'iaL;T duwnpoiir wliifli is not vt-ry 

 nnliiio or nuu-h above tiie normal liciirlit. During tlic years 

 lS0(i— 1902 the downpour was below the avera>re at Nordoernc, 

 Hronno and .Sandnessjoen. .So that we should expect to find an 

 improvement in the cod fishery in the 'rrondiijcm district and on 

 tlie coast of Nordland south of the ^'est Fiord, and statistics prove 

 that this was actually the case; for I liavc calculated, from the 

 official statistics, that the average yield in 1S86— 95 was about 2 

 millions, from 1896—1902 about .'J. In the district where the lar- 

 gest cod fishery is carried on, it is interesting to notice that there 

 was an usually high average downpour in tlie „bad" years 189G — 

 1902, while the ..good" fisiiiug seasons are characterized by vei-y 

 little downpour. And, as already mentioned, the average yield of the 

 Lofot fishery in the years 188(5 — 95 was 26.5 millions., but from 

 1896—1902 only about 16 millions. Thus, there does appear to 

 be a connection between the downpour, on the one liand. and the 

 cod and herring fisheries, on the other. 



In judging the various tislieries, a nuich too important part 

 has hitherto been given to tlie natural animal instinct, while, on 

 the other hand, it would be incorrect to attribute all the chief 

 phenomena connected with tlie fisheries to purely hydrodynamic 

 conditions. Especially Avith regard to the cod, it should be men- 

 tioned that if everything depended upon the mechanics of the water 

 layers, one would also expect to find younger individuals than fully 

 sexually developed ones at the spawning places. Dr. H.iokt has 

 shown that spawning principally takes place on the banks, less in 

 the clay channels, so that Gudiis caUarias must, undoubtedly, pos- 

 sess some degree of initiative. But it can hardly be denied that 

 the currents in the sea exert a very modifying influence on the 

 movements of the fish. From this point of view, it becomes of 

 considerable interest to have a clear knowledge of the causes of 

 these currents. But on this matter, there is no little disagreement. 

 Some scientists assert that the rotatory motion of the earth is 

 alone necessary to cause the system of currents taken as a whole. 

 But even if this be so, it can be said that the influence of the 

 rotatory motion of the earth, whether it be great or small, must 

 at any rate, be constant, and when one is trying to discover the 

 causes of fluctuations in the fishery-yield, one must especially exa- 

 mine the variable factors which may be supposed to exert some in- 

 fluence. And then, I think, the winds must first of all be con- 

 sidered. As variations in atmospheric pressure cause winds, winds 

 cause currents and currents, with great probability, exert an in- 

 fluence on the course of herrings and cod, it must certainly be 

 practical to turn one's attention to the barometrical minima. In the 

 foregoing pages, I have considered that the downpour will gener- 

 ally be influenced both by the situation and the degree of prom- 

 inence by which they are characterized. In the meantime, it is 

 interesting to consider these minima direct. 



It may now be taken for granted that the great atuiosj)heric 

 depression, which is called the winter minimum, in the Norwegian Sea 

 is subject to considerable variations, both with respect to place and 

 degree. In „The Book on Norway", Einar Haffner describes the 

 variations in atmospheric pressure in the years 1884 and lS9<i. 

 Haffner also gives charts showing the distribution of atmospheric 

 pressure, respectively in .January 1K84 and Decembei- 1890. The 



tornirr shows a low pressure north of Noiway, and the result was 

 tiiat .January 1884 was unusually mild. In the ciiart for December 

 1890, this northern minimum has disappeared, the lowpressurc centre 

 near Iceland determined the direction of the winds, and in the month 

 in question the temperature was very low over the whole of the 

 Scandinavian peninsula. In „^'mer" for 1898 (Nr. 2), Uxru 

 Pettersson has described how the great development of the Ciulf 

 Stream, in the northern part of the Norwegian Sea in the summer 

 of 1897, caused a winter minimum to the N.W. or N. of Norway. 

 In consequence of this, there was a higher average temperature in 

 Sweden in .January and February 1898, on account of the prevailing 

 westerly winds. As a whole, several winters from 1 896- onwards 

 have been unusually mild, while the summers have, to some extent, 

 been cold, at any rate, in the north. There have also been „grecn" 

 years in the same period. -Another peculiar feature in connec- 

 tion with these years, is that some arctic mammals have come far 

 south during the spring and summer (Phoca groeiilandica and 

 DelphinaptcrKs leiiras). }iut of greatest interest is the fact that 

 thei-e was a much smaller yield of cod than usual, in these years. 

 If the theory, advanced in the foregoing, be adhered to, with respect 

 to the dependence of this fishery upon winds and currents, a natu- 

 ral explanation of the decrease in the Lofot yield will be found in 

 the fact of the atmospheric winter depre.ssion in the Norwegian Sea 

 having been so marked and so situated as to make the system of 

 currents, set in motion by the wind, act as an obstacle to the pro- 

 gress of the fish. 



It is possible, too, that this way of looking at tilings, may 

 throw new light upon the subject of the changes in the heii;ht of 

 our coast water. 



According to Dr. Andreas Hansen, the variations in the height 

 of coast water have been above and below a settled medium, and 

 the result, in historical times, has been that the relation between 

 land and sea on the coasts of the North Sea and the Norwegian 

 Sea has remained unaltered. It might perhaps be practical to in- 

 troduce the idea of a medium normal height of watei', which would 

 correspond to the normal height of downpour for a given stretch 

 of coast. The medium annual height of water, according to An- 

 dreas Hansen falls into groups of years in which it is above, and 

 years in which it is below the normal height. In Røst 1891—94 

 he mentions a lesser height than usual, but in 1890 at Skagerack 

 a greater.') This answers particularly well to the circumstance 

 that on the Skagerack coast in the pei-iod 1886 — 95 there was a 

 surplus downpour, while on the northern coasts the average was 

 not attained. For, as both downpour and water-level depend upon 

 the direction and force of winds, they must have a corresponding 

 course, and the measure of the one may, therefore, serve,' to' judge 

 of the other. It is also probable that just as the water on the 

 Skagerack coast and the west coast of Norway may be in ditterent 

 phases, as proved by Hansen, so may there also be places, on the 

 long stretch of coast from Skudenes to Vardø, where the water 

 is higher than the normal height, while at others, it is lower. There 

 is reason to suppose that, in the years 1896 — 1902, the medium 

 water-level was lower than usual on the coast of Helgeland, and 

 probably also on the coasts of the Trondhjem district, for the table 

 shows that the downpour was below average. 



If events should prove that my opinion, concerning the in- 

 fluence of atmospheric pressure upon the yield from the fisheries. 



Stigning, p. .52. Norges geol. Unders. Aarb. f. 189H-99. 



