THE SALT-WATER FISHERIES OF BOHUSLAN. 211 



fessor Sars to opi^ose the general opinion that a period of spring-herring 

 fisheries had recently come to an end. Although it has not been suffi- 

 ciently proved by actual observations that the spring-herrings do no 

 longer si>awn in their usual places, this seems scarcely probable; and 

 this explanation would in no wise be applicable to the great Bohuslan 

 herring- fisheries, which, as far as known, agree with the Norwegian 

 spring-herring fisheries in all essential points. From the circumstance 

 that the summer-herring fisheries continue to be just as productive (and 

 occasionally even more so) as during those years when there were stiU 

 spring-herring fisheries, no such conclusion as the one mentioned above 

 can be drawn with regard to the latter; for it does not follow that, be- 

 cause the spring-herrings have left their old spawning-places, the sum- 

 mer-herrings should also leave the western and northwestern coasts of 

 Norway; nor does the fact that the summer-herrings remain prove that 

 the spring-herrings must do the same.^*^ Professor 8ars seems also to 

 be somewhat undecided with regard to his theory, for he has at a later 

 time, in accordance with a very general opinion in Norway, exjiressed 

 the idea that there is a direct connection between the Norwegian spring- 

 herring fisheries and the great herring-fisheries. The above-mentioned 

 opinion of Professor Sars may, however (as will be shown below, 63), 

 be developed so as to become more generally applicable ; and it is, there- 

 fore, not impossible that this very opinion contains the germ of a final 

 solution of the problem regarding the migrations of the great shoals of 

 herrings. 



58. Intimately connected with this question is the explanation of these 

 migrations from i^hysical causes. The opinion is very old that changes 

 in the physical conditions are the i^robable cause of the periodicity of 

 the herring-fisheries. The learned and thoughtful Prof. R. Strom began 

 already to see the error in the usual method of explaining the periodical 

 cessation of the herring-fisheries by human agencies, and endeavored to 

 explain the greater or less quantity of herrings, and even the fact of 

 their leaving the coast entirely, by physical causes.'"^ He mentioned, for 

 instance, that the rich spring-herring fisheries which took place during 

 his stay at Sondmor occurred at a time when the weather was very un- 

 favorable to agriculture, causing a total failure of the crops, and that 

 such failures are generally indicated beforehand by the frequent occur- 

 rence of a fish — the horngiidda — which generally lives in more southern 

 regions. Dr. P. Buhb likewise supposes that changes of weather and cur- 

 rent are the true cause of the periodical coming and going of the genuine 

 "sea-herrings" on the coast of Bohuslan. Ekstrom has explained the 

 circumstance that on the coast of Sodermanland the herrings are more 



^6 See 45 ; also, H. Strom, Sondmor, I, p. 468 ; Dansk Museum, January, 1782, p. 3-4 ; 

 A. Boeck, Om Silden, p. 130 ; A. V. Ljungman, Frelimindr lerciUeJse for 1873-74, p. G. 



'" H. Strom, Dansh Museum, January, 1782, p. 3-9. In this passage lie points out that 

 changes in the condition of the ice near the North Pole probably cause the periodicity 

 in the migrations of the herrings. 



