734 REPOET OF COMMISSIONER OF FISH AND FISHERIES. [6] 



coast far enough to take from their fisheries the character of coast fish- 

 eries. Owing to the distance, it is almost impossible, at least with sail- 

 boats, to carry on any coast fisheries on the coast of Bohuslan during 

 the period when the sea herring do not enter but pass by the Skagerack 

 on their way to the spawning grounds in the North Sea, as is the case 

 during the intervals between the Bohuslan fishing periods. I have also 

 succeeded in explaining in two new ways the secular periodicity of the 

 Bohuslan herring fisheries ; and so far all attempts to disprove my ar- 

 guments have proved unsuccessful. In the first place I have endeavored 

 to explain this periodicity by changes in the prevailing biological con- 

 ditions, consisting in a gradual change of the local fauna and flora of 

 the sea through the great masses of herring visiting these regions for 

 many years in succession ; and in the second place, by assuming a sec- 

 ular periodicity in all the outward conditions of nature prevaihng 

 throughout the entire region inhabited by herring. This last-mentioned 

 periodicity is supposed to compel the great schools of herring to move 

 from one place to the other in search of food, and also of spawning 

 places. ' It is very probable, however, in my opinion, that these two 

 causes work togethex. In giving this explanation I have also been able 

 to explain the regular changes of time and place where the sea herring, 

 during the fishing period, approach the coast of Bohuslan. By con- 

 tinuing my observations I arrived at the conclusion that the second way 

 of explaining the periodicity is probably the one which reveals its most 

 important cause, since I succeeded in showing that the Bohuslan her- 

 ring periods agreed with corresponding and well-known periods in the 

 change of weather, the occurrence of northern lights, the number of solar 

 spots, &c. ; and that the richest fisheries during a period correspond with 

 a peculiar disturbance of or change in the relation between the solar 

 spots and the temperature, which only takes place during the periods 

 when there are herring fisheries on the coast of Bohuslan, but not during 

 the intervals between the periods. These periods on an average last 

 fifty-six years ; and as several scientists, with good reason, have sought 

 to explain these periods in the occurrence of solar spots from the vary- 

 ing position of the principal planets towards the sun, it seems to me 

 that we may look in the future for so complete an explanation of all 

 these circumstances that we shall be enabled to tell beforehand with 

 some degree of certainty when these periods will occur, and in what 

 respects they will differ from each other. From what is so far known 

 relative to the Bohuslan fishing periods, 1 have considered myself justi- 

 fied in drawing the conclusion that as regards the extent of the fisheries, 

 very extensive and less extensive periods alternate. The reason why 

 the intervals between the fishing periods are not equally long must be 

 sought in the fact that the herring come near the coast at a time which 

 varies with every period, which of course also causes the fishing period 

 on the inner coast to vary in length. It may also be supposed that the 

 different fishing periods differ in another important point. Thus, the 



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